Capture Your Collections 2012 - Small Museum Version

What are digital images?

As more and more people use computers, many of the terms and words associated with them are making their way into everyday language. One of these is "digital", which is used to describe everything from digital television through to watches. The overuse of the term has undoubtedly lead to some confusion. However, for the purposes of this course we will use the term to refer to the process of creating a digital image (i.e., one existing inside a computer) from a physical object (a document, photograph or three dimensional artefact). To create a digital image we first capture the image of the original object using a camera or scanner. The image is then stored on a computer. From here it can be easily displayed on a monitor or printed. This digital image is made up of thousands, sometimes millions of pixels (picture elements).

Pixels are similar to dots on a newspaper photograph or grains on a photographic print, which are arranged according to a predefined ratio of columns and rows. Each pixel represents a portion of the image in a particular colour, or shade of grey.

Why digitize?

One of the main virtues of digital imaging is its ability to make collections more accessible. In the past if you wanted to view an object in a museum you either had to arrange to view the real thing with a curator, or view a photograph of the object. Today this process is much simpler if the collection has been digitized and recorded onto a CD-ROM or DVD, placed on a web page or in a database. Collections that were once too remote to be viewed are now accessible; objects that were once too fragile to be handled or exhibited can now be seen by broad audiences.

Digital technology helps achieve your institution's goals, whether it be highlighting particular aspects of local history or reaching a national or international audience. Digitization can also aid collections management by increasing all staff members' awareness of the content of your collections, especially if images are linked to your collections management system and networked throughout your museum. Digitized images are used in a wide range of outreach activities, including Web sites, promotional material, new products for the museum gift shop, and so on. Digitization enhances preservation and conservation strategies, since once digitization has occurred, the handling of fragile originals can be minimized. Digital images also play a role in outreach and public access, e.g., the production of exhibitions and the dissemination of information through virtual exhibitions, in galleries and through publications.

The benefits of digitization

Digitization projects are not cheap, but they should be viewed as a long-term investment for your institution and can yield substantial benefits.

Pixels and Resolution

When digital technology is used to capture, store, modify and view photographic images, the images must first be converted to a set of numbers in a process called digitization. Once digitized, photographs can be examined, altered, displayed, transmitted, printed or archived in an incredible variety of ways. As you explore digital imaging, it helps to be familiar with a few basic terms.

Digital images consist of a grid of small squares, known as picture elements, or pixels These basic building blocks are the smallest elements used by computer monitors or printers to represent text, graphics, or images.

Resolution describes the clarity or level of detail of a digital image. Technically the term "resolution" refers to spatial resolution and brightness resolution; commonly, however, the word is used to refer to spatial resolution alone. The higher the resolution, the greater the detail in the image (and the larger the file). For computers and digital cameras, resolution is measured in pixels; for scanners, resolution is measured in pixels per inch (ppi); for printers, resolution is measured in dots per inch (dpi).

Bit depth

Bit depth, sometimes called "brightness resolution", defines the number of possible tones or colours every pixel can have. The greater the bit depth, the greater the depth of colour, and the larger the colour (or greyscale) palette (number of colours). For example, 8-bit colour has a range of 256 colours (or shades of grey) and 24-bit (or higher) colour provides 16.7 million colours, but 30-bit colour has many more millions of colours, which offers higher definition and thus better results in reproducing details such as the shadowy parts of an image.

Files and file formats

Once you take a digital photograph or scan an image, the image becomes a digital file, which is stored on a computer like any other file. Image files tend to be larger than text files, since images require more data to represent visual information. The file size of an image (usually measured in megabytes, or MB) indicates the amount of data required to capture a specific image to a given level of resolution. Digital image files are stored in a variety of file formats, some specific to a given type of computer or software.

A digital image is stored as a computer graphics file allowing it to be viewed, printed, transmitted and edited. There are two basic forms of computer graphics: bit-maps and vector graphics. Nearly all digital images are stored as bit-maps and there are several bit-map file formats that you can use, including JPEG, GIF, TIFF, BMP and PNG. When deciding which of these you will use to store your digital images, it is important to consider the pros and cons of each:

See more information on compression, bitmap formats.

Exercise - Table for analyzing possible media types and resolution recommendations

Now that you better understand concepts like resolution and file format, it is time to consider how they might relate to the different types of collection materials you wish to digitize. What follows is a guide to the kinds of conversion methods and equipment, along with resolutions, you should consider as part of your preparation and research. This chart will help you decide where you should concentrate your resources. If the bulk of your collection consists of colour maps or illustrations then it may well be more cost-effective, and less time consuming, to use a flatbed scanner capable of producing 24-bit images at 300 ppi. Use the chart below to analyze what your institutional needs are. Once you have established your priorities you can then look at what equipment is available, its cost or indeed alternatives like contracting out.

Costs to consider

How much does it cost? This may be the first question you ask when the discussion turns to digitizing your collection. The answer is that cost will depend upon many issues; the size of your institution and the collection, the number of 'scanning-ready' images already on hand, how well documented your images are and, of course, your defined requirements. There really is no 'one size fits all' solution.

Whether digitizing in-house or contracting the work out, it is important to anticipate costs and budget for them. Among the various constituents of total cost for a digitization project which should be considered are:

Digitizing images: in-house vs. contracting out

When deciding on whether or not you can undertake a digitization project one of the most important considerations is whether or not the project can be undertaken by staff using resources within the museum (in-house) or using local contractors, or indeed a mix of both. When deciding which route to take it is important to consider the following advantages and disadvantages:

Contracting out: Factors to consider

Recognize that it is best not to send certain objects, such as the following, to commercial digital service providers: Original art works, fragile textiles, early printed materials, book-bindings - tooled book covers, large-format originals.

If time is of the essence and you do not already have scanning facilities and trained staff available, you may wish to consider contracting some tasks out. However, a project that is contracted out will still require some training of staff who may still need to carry out preparation, documentation and object movement work etc.

For a short-term project, you may choose to use an outside digital service provider, as a trial, with a plan to review after the first phase. If you decide to contract out you must carefully define your needs to your digital service provider. Be clear about what you want, especially in terms of size and resolution. Whether you do your photography in-house or by contracting out, it is important you include grey-scale and colour-scales in each image. You must clearly outline the need for consistent results, and set benchmarks to check the quality of the digital images compared to both the original image and the original object. Be sure to include in the contract a clause outlining action you may take in case of poor quality output by your service provider.

You may also wish to share costs by pooling your expertise and funds with other museums interested in digitizing their collection. To successfully achieve this kind of collaboration you will need to ensure you can agree on a set of imaging standards and deadlines.

If commercial service is required for scanning your collection, the following table suggests the best resolution and color specifications to better estimate the cost of scanning (an "X" in the table below indicates a recommended scan resolution for this format):

It is also worth noting that the majority of digitization projects use a combination of in-house and external contractors, who prefer to base themselves within the museum. Sometimes arrangements can be made with photographic contractors to set up a temporary studio in the museum so there will be no need to remove objects from your premises. If this is an option you will need to make sure your museum insurance, or the contractor's insurance, covers them for injury and theft or damage to equipment. Another issue to consider is the security and access to photographic equipment. Will the studio need to be packed up every day, or can it be housed in a secure area. If you have a large photographic collection, complete with its own cataloguing and filing system, it again may be easier for a contract scanner to set up temporarily in your museum. Again you will need to think about insurance.

These kinds of arrangements are contingent on having sufficient space and have the added benefit of allowing museum staff to supervise object handling. However, you will need to consider which staff will be able to assist and ensure they are available whenever the contractor may need them. Or alternatively arrange for the contractor to be on the premises only when you have sufficient staff.

Exercise

The following exercise will help you estimate the time and likely staff and equipment costs, involved in your digitization project. Most importantly it should help you determine whether or not you can afford to hire new staff or bring in a contractor. To make best use of this exercise you will need to also find out how much contractors may charge per hour. At the same time you may wish to work out an hourly cost for your own staff, as sometimes their limited time may be better spent on other projects.

Introduction and disclaimer

The purpose of this module is to examine the legal issues surrounding the reproduction and digitization of heritage content. In particular, it will focus on the law pertaining to copyright of digital photographs. However it is important to note that this module does not examine the law pertaining to the exhibition, transmission or communication to the public of digital images.

This module is written from the Australian and Canadian perspective and provides only general information. Neither the Canadian Heritage Information Network (CHIN) or Australian Museums On Line (AMOL) seek to provide legal advice through it. If such advice is required it is strongly recommended that the services of a competent professional, licensed to practice law in your jurisdiction should be sought. The governments of Canada and Australia assume no liability whatsoever with respect to actions that may arise as a consequence of using this guide, either by negligence or otherwise. As such it is important for you to understand that any statements contained herein should not be construed as being either the official or unofficial policy or statement of legal position of any entity of the governments of Canada or Australia. They are simply broad guidelines.

Copyright Law 101

Copyright protects the expression of ideas that are fixed in any media. It also protects the majority of creations, including literary, dramatic, musical and artistic works, sound recordings and audio-visual works. Ordinarily photographs are considered to be artistic works and thus the author (photographer) is the copyright holder. However this may not be the case where works are created in the course of an employee's duties or where copyright has been assigned in writing to someone else.

See more information on Canadian rights, exceptions to copyright, rights management and protection technologies.

Copyright licence

Before you digitize a work in your collection, it is advisable to determine first whether you have the right to make the digital reproduction. It is important to note that just because you may legally own an artwork, object, or photograph and have a donor receipt, this does not necessarily mean you own copyright. The same can be said of object loaned or copies of objects that you may have in your collection. Because they are in your collection does not necessarily mean you own copyright to images of them.

Below is a basic checklist that will assist in obtaining the appropriate clearances. It is by no means exhaustive, and proper legal counsel should be consulted to ensure that you hold all appropriate clearances before reproducing the work, or the photograph of the work or compiling it into a database.

Legal protection available

As a matter of course, all digitized images that are copyright protected should have a copyright notice displayed somewhere on the image or below it, to remind the viewer of the work's copyright status. Such notices commonly take the following form:

Copyright © 2012, Name of Copyright Holder. All Rights Reserved.

If you place your digitized image on the Internet or include it in a database where either a public or limited audience, such as via subscription, can view it, you may want to include Rules of Use for your images. Where copyright law may fall short, Rules of Use have become the common way of closing this legal gap. Rules of Use, appropriately placed between the home page and subsequent pages of a Web site or virtual exhibition, provide an implied contract with the visitor. In other words, if the visitor to the Web site has no choice but to scroll through the rules before continuing to browse through the Web site, then it is arguable that the visitor is bound by the rules as an implied contract. The argument is strengthened where a click-through button is provided so that the visitor can indicate whether he/she agrees or disagrees with the Rules of Use. If the visitor disagrees with the terms, access to the content on the Web site is denied.

It is highly recommended that Rules of Use be established for any Web site or virtual exhibition containing copyrighted digitized images. It is also recommended that the Rules of Use contain contractual provisions acknowledging copyright protection and conditions upon subsequent use or reproduction.

Digital watermarking

If you intend using your digital images to produce high resolution (quality) images for a website or other digital products, you may wish to use specialized software to protect your image copyright. One of the most common ways to deter people copying your images without your permission, is to add a digital watermark to the images. This kind of technology is particularly useful if you intend placing images of contemporary artworks on your website where you may be required to protect not only your own museum's copyright, but also the artists'. Also called digital finger printing, watermarking allows you to encode a subtle or not so subtle mark within your digital image files so that when copied the file cannot be altered or the mark removed. Depending on the technology used, this mark can include the name of the copyright owner or their logo. Be careful, digital watermarking software can be expensive and you need to carefully assess the real risk against the cost of implementing an effective solution.

Points to consider

• Do you hold copyright for objects and the images you plan to digitize?
• Have you consulted legal counsel regarding any issues pertaining to copyright on your objects or images?
• Are you aware of the moral issues related to cropping or otherwise altering images?
• Are you planning to put a "Rules of Use" statement on your electronic image database?
• Do your "Rules of Use" precede viewing images?

Introduction

The type of data accompanying digitized materials determines how they can be searched, sorted and displayed. Museums are more capable of managing their collections when they use proper database management technologies and documentation in conjunction with digital imaging projects.

Metadata

The images produced in a digitization project contain valuable data - or information - about the objects which have been photographed. Metadata may be defined as data about this data. It is important to distinguish three main types of metadata:

• data about the subject content of the image - which tells what the image is about and what interpretive significance it may have.
• data which categorizes the image within a system of subject headings - which is needed to locate, retrieve and handle the subject content
• data about the technical characteristics of the image - which is needed to determine computer equipment and software requirements for retrieval, handling, storage and suitability for use in particular interpretive products.

Metadata includes all cataloguing or indexing information created to arrange, describe and otherwise enhance access to an information object. In other words, meta-data describes your digital images and gives them meaning, context and organization. It also facilitates access to the content of the image and technical information about it.

Descriptive metadata (content information) is information about the object captured in the image. CHIN's data dictionaries and other related documents on content standards are schemas that can help a museum determine what type of content meta-data it needs to record, and how to record it.

Describing the object

If you already have a computerized collections management system, you may already have textual information describing the object; digital images will add value to your system. In order to provide good information, you should be aware of structural standards and content standards. The former will define the fields you use to describe an object; these may be predefined by your collections management package. The content standards define or provide guidance for the information you will put in the fields. Data structure standards, such as the CHIN Data Dictionaries, provide guidelines to assist in determining what fields of information you should include in your collections management system. They also describe the format in which to enter the data. If you are creating an image database separate from your collections management system, you will want to ensure that this information is consistent. Generally speaking, you should consider displaying the following fields with your record. The following list, taken from CHIN's Data Dictionary for the humanities, includes the record fields you may wish to display with an image. Think of it as the text accompanying an object in your museum. No doubt you have standard fields of information on every object on display. Remember that people looking at your information online do not necessarily follow physical groupings as they are naturally set out in a museum. Even if your online information is grouped online by theme, artist, style or period, it can normally be viewed in any order a viewer may choose; therefore you must provide as much contextual information as possible.

• Object Name
• Object Type
• Title
• Artist/Maker or
• Manufacturer
• Materials
• Technique
• Dimensions (height, length, width, depth) HT/LE/WI/DP
• Subject
• Date: (CHIN Date of object from; Date of object to; production date; School/Style)
• Cultural Context
• Description
• Artist Birth Date
• Artist Death Date
• Institution
• Copyright Details
• Origin Country
• Origin Province

See more information on metadata and how it should be used to describe the image.

Image standards & guidelines

Many of the existing studies conducted to determine optimum image resolution and image file formats indicate that the higher the image quality, the greater the longevity of the images. Choosing a common process and format when digitizing a collection will greatly facilitate subsequent image processing. Only the master images should be used to create subsequent surrogate images.

The image capture process should produce digital images of the highest quality feasible in terms of resolution and colour depth. These are the master or archival images, and should be stored in an offline mode or kept accessible in read-only mode. Ordinarily these master images should be accessed infrequently, kept in the original format and used only to create surrogate images.

From master images and surrogate images, working copies can be produced for a variety of purposes. However it is important to remember that different applications require images of varying quality. Consequently if you require Digital images for visual references in an electronic database, such as the World Wide Web, they need only be low-resolution formats. So a copy of a surrogate image would suffice. Digital images used for high-quality printing, however, will require a substantially higher resolution image. To do this you may need to access the master image. However if this is a common request then you should consider producing surrogate images of a relatively high resolution and use these instead of continually accessing your masters.

To ascertain the quality required for digital imaging, it is first necessary to determine the intended uses for the images. The most common use for digital images is to make them available over the World Wide Web, via a collections management system, as low-quality, thumbnail images. Also of importance, is digital reproduction for printing or digital preservation. These larger or more detailed reproductions require images of higher quality. Specialty uses of images for conservation work, detailed analysis of works of art, etc. require substantially higher quality images.

See more information on preservation and storage standards and guidelines.

See more information in a sample image record in the Getting Started module.

Do you understand:

• What object information you should record and why?
• What image information you should record and why?
• What strategies you need to preserve your images?

The importance of planning

Most museums take a 'project' approach to digitization, while others systematically digitize all or large parts of their collections. Whichever approach you adopt, planning is critical to the success of the project. The Claremont Museum in Perth, Western Australia, systematically digitized its collection of 2,000 historic photographs of the town. The project took twelve months and used the services of an external contractor who scanned photographic negatives to produce a CD-ROM. To effectively coordinate efforts staff devised a detailed plan that not only outlined when certain tasks were to be undertaken but also, by whom. It was important from the beginning to undertake a skills audit to determine what volunteers were capable of doing, and training was provided, where necessary.

Whether or not your project aims to digitize all or only a part of your collection, before proceeding, you need a plan. Very basically this plan should detail what will be digitized and in what order. But even before this plan can be developed you need to undertake an audit of resources you have, or may need to purchase. Ordinarily successful digitization projects require a range of resources, including the following:

• Trained personnel,
• Digitization technology and equipment,
• Physical space sufficient for the process,
• Funding.

Defining audiences

Before a single image is digitized, the intended users of the images, both inside and outside your institution, should be determined. Furthermore, this audience should ideally be involved in the development of the project brief to ensure that their unique likes, dislikes and skills are taken into account.

The project leader should interview staff members, volunteers and others who will use museum images, asking about not only immediate uses, but future ones as well. If the primary intent of the digitization project is to increase public access to your collection you should consider placing images on your web site or on a museum public access terminal. Alternatively they could be used in the creation of a CD-ROM, DVD, or publication.

Evaluating assets

Some museums have thousands of photographs and objects and sometimes it can be difficult to decide which should be digitized first. To develop a priority listing it is often useful to consider the following questions:

• What objects have already been photographed?
• What documentation is available?
• Is copyright cleared?
• Existing images are in what formats?
• How are the images stored?
• What is the quality of the images?
• Are digitized images from a previous project available?
• At what resolution have the digital images been stored?

A survey of all of the photographic holdings of your institution should be carried out to determine not only what images are held in different parts of the institution but also in what formats these images are currently available.

Next is an assessment of the images currently available. Digitizing already available images, such as colour transparencies, will be a less costly and time-consuming process than beginning 'from scratch'. Some objects will need to be re-photographed if the images on hand are in poor condition or are not good representations of the original object. Ideally only good, professionally photographed images created with a colour bar or grey scale should be digitized. If previously created digital images are available, be careful to consider whether the quality is high enough for your current needs, and whether the associated documentation is adequate. New photography will add significantly to the time and money required for a digitization project, particularly when the objects to be photographed require significant preparation time.

Prioritizing work

Even if the long-term goal is to digitize the entire collection, the project will probably be done over time in accordance with financial and staff constraints. To achieve this, all work needs to be prioritized according to the project plan previously defined. Generally, priority should be given to the following:

• Images for which you have copyright clearance,
• Iconic images significantly associated with your institution,
• Images for which you have good documentation,
• Objects used in exhibits, current or upcoming,
• Images of the museum that could be developed into a virtual tour or promotional publications,
• New acquisitions,
• Well-formed collections of particular significance or special public and/or educational appeal,
• Images following a particular theme or subject area,
• Natural groupings in your collection.

Resources & reducing costs

Occupational Health & Safety

It is very likely that when setting up your digitization project you will install one or more computer workstations. The way you design these workstations needs to be carefully considered so staff and contractors can work without discomfort or risk of injury. There are many web-based resources that can help you with the design of this environment; one of the best is Cornell University's Ergonomics website. Here you will find a comprehensive overview of the dos and don'ts of designing a computer workstation.

Exercises

There are two exercises in this section. One will help you develop an overall project plan. The second will be useful to those institutions with extensive photographic holdings as it will help you analyze the status of your photographic collection.

Capturing Images

One of the first steps is to determine what in your collection is to be digitized. The types of materials selected for digitization will determine the imaging equipment used. Image capture from objects by a digital camera is a time-consuming process and may require substantial resources. A thorough inventory should be made of existing photographic or film-based materials such as slides and prints to determine whether any of this material can be used for the digitization project; digitizing photographic materials may be preferable because of lower costs if the required results can be attained. Tests should be done on each format to determine the results.

Hardware & software

It is easy to be overwhelmed by the wide selection of digital imaging hardware and software available. However there are many very successful examples of small scale digitization projects that used very basic equipment to successfully digitize collections. Even so, research of software needs and equipment should be carried out, and careful attention should be paid to the following factors:

Computers

Scanners

Flatbed scanners : The most popular image capture device for capturing images, the flatbed scanner can be used to capture opaque objects and transparent materials such as 35-mm slides (if equipped with a slide scanning feature) unless the quantity of transparent materials warrants a separate film scanner.

The following are some of the features to consider:

Film scanners : Dedicated film scanners may be required if large quantities of transparent materials are to be scanned. Although more expensive than a flatbed scanner, a film scanner will generate a higher quality image because its scanning process is specific to this medium. While it is expensive, a film or slide scanner will produce the highest quality digital images. Some film scanners are capable of capturing larger transparency formats, thus producing very high quality digital images. An alternative to a film scanner is a flatbed scanner with a transparency media adapter (TMA). This method will not produce as high a quality a product as the film scanner, but may be sufficient for your needs. The following are some of the features to consider:

See more information on scanning images.

Digital cameras

Digital cameras : The decreasing cost of high-end digital cameras, coupled with their improved performance and reduced production time has rendered traditional film cameras obsolete for the purposes of content digitization. Virtually all new digital cameras at any price point are capable of producing images suitable for web publication. However, to properly reproduce details in larger formats (for advertising copy, or for the conservation of detailed visual information about the original object) sufficient optics and resolution are necessary. As a general rule, high-end digital cameras are more expensive than flatbed scanners, but less expensive than a film scanner. When buying a digital camera the following are features to consider:

See more information on digital cameras.

Digital cameras can be used to capture many of the same formats such as prints, documents, large maps, etc. For some items, a digital camera may be more appropriate than a scanner, whereas a scanner may be better suited for capturing other objects.

See more information on scanners vs digital cameras.

Traditional film

While it is possible to capture images of two and three-dimensional objects using traditional film cameras, then to have them digitized either at a photo lab, or by doing this yourself with a flatbed scanner, the process is tedious and expensive on a per-image basis, and will become increasingly difficult as suppliers and support for film-based equipment dwindles. If your institution has no budget for a digital camera, already has a photographic process using film in place, can justify the additional labour required to develop (and possibly re-shoot) film images, and has only a limited number of high-resolution images to produce, then you may want to continue using the traditional film format in the near-term. Otherwise, unless your digitization project requires large film format (for specialised applications), there is no benefit to using traditional film to digitize museum collections.

Imaging software

Although several types of freeware and shareware products are available on the World Wide Web, to optimize images, high-end commercial imaging software such as Adobe PhotoShop should be used. During the image capture process, little or no image enhancements should be made to the master images created for archival purposes. This will ensure that the consistency of the image capture process is retained and will match the recorded information (metadata).

Imaging software should be able to handle all the necessary manipulation of images that is required. The following are some of the features to consider:

• Import and export file formats
• Operations such as cropping, brightness/contrast adjustment, resizing
• Multiple images open at a time
• Ability to handle large size images
• Multiple undo levels
  

  

• Batch and macro facilities for repeat operations
• Software interfaces for scanners and digital cameras
• Save workspace settings to pick up work in progress where it was left off
• Built-in image management
• Cross platform operation

See more information on image manipulation software.

Printers

There are a range of printers on the market, many of which approach the level of quality you get from traditional photofinishers. However, you need to choose a printer whose capabilities match your needs.

As with cameras and scanners, resolution is the key issue for printers. To print photos, your printer should produce output at 600 dpi or better. High resolution printers produce images that are more realistic and are better at capturing details from your digitized images. Ideally, your printer should be capable of outputting images without sacrificing quality, colour accuracy and resolution.

Getting the best possible image from your printer requires supplies or material that are optimized for that printer or printer technology (e.g. printing inks). In many ways, the paper or transparency film (for overheads) you choose is as important as the printer you select, since creating the best image requires high-quality materials.

See more information on printing images.

Exercise

When you photograph or scan any collection items, it is crucial that a range of image details are recorded on an Image Production Record. The process of recording these details will act as a quality control mechanism and ensure that the equipment is correctly calibrated each time. The recorded information will also allow for the production of further identical images, should the need arise, as all the crucial settings will be known. As a way of familiarizing yourself with this process you may wish to take a sample set of between ten and twenty potential images and see if you can fill in the following details:

Introduction

Having spent considerable time, effort and money producing often thousands of images it is of the utmost importance that the images are correctly stored and cared for. Like any asset, digital images can be misplaced, damaged or simply inaccessible because of hardware or software obsolescence. The quantity of data produced by typical small museum imaging projects means that management of the images becomes an important consideration for both current activities and future planning. As such, planning for digital imaging projects should ideally include a policy for managing the assets once they have been created.

The image capture process will create master images which ideally should be stored on archival format devices with at least one copy stored off-line or semi-online mode. Normally one or more surrogate images will be created from the master images for output purposes such as Web display. The management of the master and surrogate images will require careful planning to ensure that proper access is maintained. This information can be recorded in an image catalogue or database linked to or integrated with the existing collections management database.

To ensure there are no confusing mix-ups between surrogates and master images, image-naming guidelines should be developed to record and keep track of images. For example you should consider developing a prefix or suffix descriptor to identify each surrogate image e.g. car-P1037-Sur.jpeg. The Sur identifies the image as a surrogate and the object registration number tells us exactly what the picture is. It is also a good idea to include a single word identifier like car, painting, jacket etc. If you happened to misplace your car image this would then save you from having to open all your image files.

Master images

The image capture process is resource intensive. Storage requirements at this stage of the creation process are likely to be very high, depending on the number of images involved, in terms of both hard-disk/server space for work in progress and back-up local archive media, whether on local, networked or portable media. Following a review and recording process, the master images will normally be transferred periodically to a long-term archival format such as an optical medium. If local archive copies of primary acquisition or master/archival files on portable media are maintained, it is essential to store them under the right conditions, identify them properly and have a strategy in place for their long-term survival.

Surrogate images

Surrogate images are subsequently created from the master images for a variety of purposes. Images used for visual references in a Collection Management database or the World Wide Web, require a low-resolution display format such as 500 x 500 pixels. An even lower image resolution of 150 x 150 pixels may also be required for thumbnail access. Digital images used for high-quality printing will require a substantially higher resolution. An 8"x10" hard copy printed at 300 dpi will require an image file with a resolution of 2400 x 3000 pixels, enhanced for high-quality printing. Each type of surrogate image may require different image editing and enhancement processes.

Less storage is required for surrogate images than for master images. Online and networked access to these images will probably be an important requirement. The image capture phase is when you should also be producing your surrogate images; consequently you need to factor in additional time and storage space.

Backup copies

An often neglected aspect of any image management and storage planning process is the provision for backup copies of both master and surrogate images. As with any situation, disasters can happen, from the destruction of the entire digital storage area to much smaller problems such as read errors on a CD-ROM. Backup procedures for surrogate images will likely be in place if these reside on a file server accessible through the network. However, master images stored on an archival format, such as CD-ROM or tape, should be backed up to create a second copy which should be stored separately from the originals. The backup format can be the same as the original or another format.

Storage devices & media

Planning for the storage devices and storage media must be an integral part of any digitization project owing to the relatively high storage requirements for digital images. For even an image project of 1,000 objects with an average file size of master image of 30 Megabytes (MB) each, it is clear that considerable storage facilities will be required.

The storage devices selected for the digitization project may be a combination of different types and formats depending on the uses and access methods required. Other storage devices can be added during the project as volumes warrant.

The 3-2-1 Rule

This best practice is commonly used for in the backup of all forms of data, and it applies well to digital images. The rule states that:

• Three copies of your organization's data should be kept, including one version used for primary access, and two backup versions.
• Two forms of backup (storage) media should be used.
• One copy of the data should be stored offsite.

Types of storage media

Quality control

Throughout the process of digitization it is essential that from time to time you check processes, documentation and product quality to ensure that technical, or record management errors or oversights, are picked up early and not replicated across the project. A common problem, not often picked up until the end of a project particularly if an external contractor is being used, is the resolution at which images are being scanned and stored. A check, early on and regularly thereafter, could save considerable time as well as money. Here again the need for clear and documented instructions is particularly important for external contractors.

Do you understand:

• The difference between master and surrogate images?
• The importance of making back-up copies of master and surrogate images?
• The importance of using a naming convention to identify your image files?
• Which kind of storage device will be most suitable for storing your digital images?

Plan 1

If you have limited time and would like a brief overview of the issues, costs and resources needed for a digitization project, please see the following:

• Introduction
  • What are digital images
  • Why you should consider digitizing your collection
  • The benefits of digitizing your collection
• Fundamentals
  • What digitization equipment and resolution is appropriate for different collection items
• Costs
  • The variety of potential costs you should consider
• Planning
  • What resources a digitization project requires
• Legal issues
  • How copyright legislation affects digitization projects

Plan 2

If you have limited time and would like a brief overview of the issues, costs and resources needed for a digitization project, please see the following:

• Costs
  • The variety of potential costs you should consider
  • The benefits and pitfalls of in-house vs contracting out services
• Planning
  • What resources a digitization project requires
  • What you need to consider before beginning a digitization project
  • How to determine priorities for digitization

Plan 3

If you need to decide whether or not to buy a camera, flat bed scanner or film scanner, we suggest you use the following course resources:

• Getting Started
  • Film photography vs. digital photography
  • How a scanner works
  • How to choose a scanner and printer
  • What equipment is available and what equipment is needed for different projects

Plan 4

If you need a brief overview of the legal and copyright issues pertinent to a digitization project, the following will be useful:

• Legal issues
  • How copyright legislation affects digitization projects
  • How to go about attaining copyright clearance
  • What "Rules of Use" are

Plan 5

If you have already purchased hardware and software for a digitization project and are wondering what to do next, we suggest you view the following:

• Introduction
• Fundamentals
  • What images and formats you can use
• Planning
  • How to determine priorities for digitization
  • What occupational health and safety issues you should consider
• Getting started
  • How to manipulate a digitized image
  • What equipment is available and what equipment is needed for different projects
• Standards
  • The use of metadata related to images
  • Image standards and guidelines
  • Preservation and storage standards and guidelines
• Managing Images
  • The use of master images
  • The use of surrogate images
  • The importance of storage devices and media
• Legal issues
  • How copyright legislation affects digitization projects
  • How to go about attaining copyright clearance
  • What "Rules of Use" are

Plan 6

If you are preparing to photograph 3D objects the following will be useful:

• Introduction
  • What are digital images
  • Why you should consider digitizing your collection
  • The benefits of digitizing your collection
• Fundamentals
  • What images and formats you can use
• Costs
  • The variety of potential costs you should consider
  • The benefits and pitfalls of in-house vs contracting out services
• Planning
  • How to determine priorities for digitization
  • What occupational health and safety issues you should consider
• Getting started
  • How to manipulate a digitized image
  • What equipment is available and what equipment is needed for different projects

Plan 7

If you have already produce a number of digital images and wondering what to do next the following will help you:

• Standards
  • The use of metadata related to images
  • Image standards and guidelines
  • Preservation and storage standards and guidelines
• Managing Images
  • The use of master images
  • The use of surrogate images
  • The importance of storage devices and media
• Legal issues
  • How copyright legislation affects digitization projects
  • How to go about attaining copyright clearance
  • What "Rules of Use" are

Plan 8

If you are preparing a presentation to persuade a sponsor, trust or board of the merits of digitization, the following course resources will be useful:

• Introduction
  • What are digital images
  • Why you should consider digitizing your collection
  • The benefits of digitizing your collection
• Fundamentals
  • What digitization equipment and resolution is appropriate for different collection items
• Costs
  • The variety of potential costs you should consider
• Planning
  • What resources a digitization project requires

0-9

35 mm equivalent

Field of view on a digital camera stated as an equivalent focal length on a 35 mm film camera. For example, a 5 mm lens on a digital camera is equivalent to a 36 mm lens in the 35 mm system.

A

algorithm

A rule (often mathematical) governing computer processes; here, those used in file compression.

A-D Converter

The analogue to digital converter converts the analogue signal originating from the image sensor in a digital camera or scanner to a digital signal.

archival image

A digital image, also referred to as a master image, that has been captured at the highest practicable quality or resolution and stored for long-term usage. Archival images are normally stored in an off-line mode on tape or CD and are accessed only for the production of surrogate or derivative images.

area array

A common type of detector (see CCD and CMOS) arrangement within a digital camera; contains a fixed number of horizontal and vertical pixels.

artifacts

Visual digital effects introduced into an image by electrical noise during the capture process or over-compression that do not correspond to the original image being scanned. Artifacts might include pixellation, dotted or straight lines, regularly repeated patterns, moiré, etc.

autofocus

The camera automatically focuses on the object to capture at which it is pointed; this object then becomes the sharpest part of the overall image.

automatic sheet feeder

A device attached to a scanner, printer or photocopier that makes it possible to process large numbers of documents automatically.

B

bandwidth

The transmission capacity of a communications channel; data speed measured in bits per second. A high-bandwidth network is required for fast transfer of image files, as they typically contain large amounts of data.

benchmark

The set of tests normally done during the feasibility study, to determine the technical standards to which the material should be digitized. Quality assurance procedures should measure the digitized images against these benchmarks.

bit

Short for binary digit, the smallest unit of data in computer processing. A bit can represent two values: on and off, or 1 and 0.

bit depth

Also referred to as colour depth is the number of bits used to describe the colour of each pixel. Greater bit depth allows a greater range of colours or shades of grey to be represented by a pixel, e.g.:

• 1 bit is black or white (on or off)
• 8-bit grayscale is 256 shades of grey
• 8-bit colour is 256 colours
• 16-bit colour is 65,536 colours
• 24-bit colour resolution is 16.7 million colours
• 30-bit or higher colour is billions of colours

bit-map graphic

Also referred to as a raster graphic; a method of storing information that maps an image pixel. The bitmap image consists of rows of pixels.

BMP

Standard image format Windows-compatible computers. The BMP format supports RGB, indexed-colour, greyscale, and bitmap colour modes.

brightness adjustment

The addition or subtraction of white light to a colour.

brightness resolution

Defines to what resolution a single pixel's intensity can be expressed

byte

A quantity of digital data, consisting of 8 bits, the basic unit of data used in information science.

C

calibration

The process of adjusting the colour of one device relative to another, such as a monitor to a printer, or a scanner to a film recorder, or the process of adjusting the colour of one device to some established standard.

capture devices

These include flatbed scanners, drum scanners, film scanners, digital cameras. They use electronic devices rather than photographic film to capture images.

CCD

Charge-Coupled Device; a light-sensitive chip or image sensor used in scanners and digital cameras that converts light into proportional (analogue) electrical current. The A-D converter converts analogue signals into pixel values.

CCITT Group III or Group IV

The standards adopted by the International Telecommunications Union (ITU), formerly the Comité consultatif international de télégraphique et téléphonie (CCITT), to compress text page images. All fax machines in common use employ one or both of these standards.

CD-R

A Write Once Read Many (WORM) optical disc, although the whole disc does not have to be entirely written in the same session. Current storage capacity is 650 Megabytes. Estimated lifespans vary widely with properly stored archival (gold) discs exceeding 100 years.

CD-ROM

Compact Disc Read-Only Memory. A form of disc-based, random-access data storage, usually mass-produced and distributed as a publication. Information is pressed on these discs at the time of manufacturing. Computers can read, but not write to them. At present, capable of holding up to 900 megabytes of data.

CD-RW

A type of optical disc that can be re-written to multiple times. Storage capacity is comparable to CD-R. Lifespans are typically short (under 10 years).

CMD

Charge Modulated Device, an active image sensor derived from CCD pixel technology and CMOS transistor technology.

CMOS

Complementary Metal Oxide Semiconductor is another type of image sensor found in a digital camera. Pixel sensitivity is lower than the CCD sensors and usually has more noise in the imaging device.

CMS

Colour Management System; a collection of software tools designed to produce consistency in the representation of different colour capabilities of scanners, monitors and printers to ensure consistent colour throughout the image production process.

CMYK

A colour model using cyan, magenta and yellow pigments as the subtractive primary colours along with black (K), used primarily in the printing process. Combining the CMY inks at full saturation renders black (subtracting all colours).

colour accuracy

Fidelity of the scanned image's colour to that of the original.

colour correction

Altering colours as they appear in a digital image or in print to ensure that they accurately represent the work depicted.

colour depth

Also referred to as bit depth is the number of bits used to describe the colour of each pixel. Greater bit depth allows a greater range of colours or shades of grey to be represented by a pixel, e.g.:

• 1 bit is black or white (on or off)
• 8-bit grayscale is 256 shades of grey
• 8-bit colour is 256 colours
• 16-bit colour is 65,536 colours
• 24-bit colour resolution is 16.7 million colours
• 30-bit or higher colour is billions of colours

colour look-up table

A table containing the RGB values for 256 colours. Storage space is saved as an 8-bit number links each image pixel to a RGB value held in the table rather than having each pixel hold a 24-bit description of its colour.

colour scale

A table containing the RGB values for 256 colours. Storage space is saved as an 8-bit number links each image pixel to a RGB value held in the table rather than having each pixel hold a 24-bit description of its colour.

colour separation

A process of converting full-colour images into a limited number of primary colors. Additive primary colours (red, green and blue) are used by the scanner, and the subtractive primary colours (cyan, magenta and yellow) plus black are used for printing press colour separation.

colour space

Mathematical definitions of colour used for aiding communication of colour information; means of representing the spectrum.

compactFlash

Storage card used in digital cameras to store captured images. The CompactFlash can be erased when the images have been transferred or are no longer needed.

compression

An algorithm applied to a digital image to reduce its file size. Compression techniques are distinguished by whether they remove detail and colour from the image. Lossless techniques compress image data without removing detail; lossy techniques compress images by removing detail.

continuous tone

An image whose brightness appears consistent and uninterrupted. Each pixel in a continuous-tone image file uses at least one byte each for its red, green and blue values. This permits 256 density levels per colour, or more than 16 million colours.

cropping

A method of discarding extraneous material from a digital image e.g. borders created during the scanning process.

D

derivative image

An image that has been created from another image, such as the archival image, through some kind of image editing process to create a user or working copy. The process usually involves a loss of information to reduce the size by sampling it to a lower resolution, using lossy compression techniques, or altering an image using image processing techniques.

descreening

Software functions build in to some scanning software applications to reduce or eliminate moiré patterning (unattractive stripes or diamond patterns appearing on the scan).

device driver

A software utility designed to tell a computer how to operate an external device: for instance, to operate a printer or a scanner, a computer will need a specific driver.

Digital Audio Tape (DAT)

Magnetic recording tape manufactured to hold audio recordings in digital format. However, due to the large storage capacity of a single tape, the medium is often used for general computer data storage.

digital camera

A camera that contains no film but records images as digital objects which can then be downloaded into a computer for further processing.

digital image

A matrix or image composed of pixels whose locations hold digital colour and/or brightness information which, when viewed at a suitable distance, form an image.

digital imaging

A term generally used to describe the process of creating and manipulating digital images.

Digital Linear Tape (DLT)

Magnetic recording tape manufactured to hold digital format files. Correctly stored this format can retain content as long as 30 years. Storage capacity equals or exceeds that of digital audio tape.

digital preservation

The long-term maintenance and upgrade of digital files on digital storage medium

digital watermark

A visible or invisible watermark that is applied to a digital image such that ownership of the image is known.

digital zoom

An electronic enlargement of part of the image making it appear closer and bigger, simulating a telephoto lens. The image is actually being cropped, resulting in loss of surrounding pixels and resolution. In some digital cameras and scanners, interpolation is used to offset this loss.

digitization

Also referred to as image capture, is the process of creating a digital representation or image of an original through scanning or digital photography.

dithering

A process in which software or an output device simulates continuous tones with groups of dots.

DNG (Digital Negative)

An open, RAW digital photography image format, released by Adobe in 2004, with the goal of improving long-term access to RAW images. As of 2012, Adobe has submitted the DNG format for ISO certification. If successful, this format will likely be taken up to a greater extent. In the interim, a number of smaller camera companies have adopted use of the DNG format, but major camera manufacturers continue to rely on proprietary RAW formats. Accordingly, Adobe has reverse engineered major manufacturers' RAW formats so that these can be converted losslessly to DNG. This has worked to some extent, although it appears that DNG files converted from some proprietary RAW formats will not work in all editing software supporting the DNG format. Test your workflow before wholesale adoption of a system that archives DNG files converted from proprietary RAW formats.

dpi

Dots per inch; measurement of the resolution of an image output device. DPI expresses the number of dots a printer can print per inch, or that a monitor can display, both horizontally and vertically. The term is often conflated with pixels per inch (ppi).

dram

A type of random access memory (RAM) often used in computers. DRAM is one of the simplest forms of random access memory to physically implement, and because of this, more information can be stored in a given space.

drum scanner

A high-quality image-capture device. The image to be captured is wrapped around a drum that spins very fast while a light source scans across it to capture a digital version of the image.

dvd (digital versatile disc)

A digital optical disc storage medium offering higher storage capacity than compact discs (CDs) while having the same dimensions. As with CDs there are various types; DVD-R offers a lifespan of 2-15 years, and can hold up to 8.5 Gigabytes of information.

dye sublimation

A type of printing process in which a dye ribbon is heated by the print head, creating a gas that hardens onto special paper. This creates soft-edged spots of colour that melt into each other and give the appearance of a continuous-tone photograph.

dynamic range

The ratio of the saturation to noise, limited by the bit depth of the sensor. Dynamic range is expressed numerically (3.0, for example). In the captured image the dynamic range relates to the colour fidelity and contrast range of the picture. The greater the dynamic range, the higher the contrast and colour bit depth.

E

F

file

A collection of information, such as text, data or images saved on a storage device such as a disk or hard drive.

file format

A type of format for encoding the information in a data file. Some common image file formats include TIFF, JPEG, and BMP.

film scanner

Scanner specifically designed for capturing transparent film formats such as 35 mm film by mounting film in a holder that may be automatically drawn through the device.

FireWire

A very fast external bus that supports data transfer rates of up to 400 Mbps developed by Apple, FireWire falls under the IEEE 1394 standard.

fixed focus

The camera's focus is pre-set to a distance at which most subjects or objects will be in focus. Not as precise as autofocus.

Flash

An electronic non-volatile computer storage medium that can be electrically erased and reprogrammed.

FlashPix

An image format developed by Kodak, Hewlett-Packard, Live Picture and Microsoft which offers multiple-resolution storage, and JPEG compression.

flatbed scanner

An image-capture device in which the source material remains stationary while the sensor (usually a CCD linear array) passes over or under it. Sometimes called a reflective scanner.

focal length equivalency

Lens specifications for digital cameras given in 35 mm camera lens equivalents (since most users are familiar with 35 mm lenses).

G

gamma

The relationship between the voltage input and the brightness of a monitor. An important factor in calibration as monitors have to compensate for gamma to get the desired on-screen grey values. The standard gamma on Windows is 2.2, and on Mac 1.8.

gamut

The total range of colours reproduced by a device. A colour is said to be "out of gamut" when its position in one device's colour space cannot be directly translated into another device's colour space. A typical CMYK gamut is generally smaller than a typical RGB gamut.

GIF

Graphic Image File format, a widely supported image-storage format promoted by CompuServe that gained early widespread use on online services and the Internet. Resolution is limited to 8-bits, or 256 colours. gif89a is a more recent format that supports interlacing.

gigabyte (GB)

A quantity of digital data. When referring to disk space or transmission rates for such data, one gigabyte is equivalent to 1 billion (109) bytes. When referring to computer memory for such data, the term often refers to its slightly larger, historic definition of 1,073,741,824 (230) bytes.

greyscale

The brightness of a pixel expressed as a value representing it's lightness from black to white: Usually defined as a value from 0 to 255, with 0 being black and 255 being white. A term used to describe an image containing shades of grey as well as black and white.

H

halftone image

An image reproduced by means of a special screen made up of dots of various sizes to simulate shades of grey in a photograph; typically used for newspaper or magazine reproduction of images.

handheld scanner

A hand-held, generally low-quality, device for digitizing images.

histogram

An analysis tool consisting of a bar graph that can be used to identify contrast and dynamic range image problems. Histograms are found in high-end imaging software used to manipulate digital images.

hue

Used to describe the entire range of colours of the spectrum; the component that determines just what colour is being used.

I

ICC

International Colour Consortium established by industry vendors to create, promote and encourage the standardisation and evolution of an open vendor-neutral, cross-platform colour management system architecture.

ICC device profile

A file that describes how a particular device (e.g., monitor, scanner, printer) reproduces colour in its specific colour space. Profiles can be either generic or custom.

image capture

Also referred to as digitization, is the process of creating a digital representation or image of an original through scanning or digital photography.

image database

Computer system where image files are kept in an organised form. Software that facilitates organised storage and retrieval of digital images.

image formats

A type of format for encoding the information in a data file. Some common image file formats include TIFF, JPEG, and BMP.

image manipulation

Modification of images such as tonal adjustments, cropping, moiré reduction, etc. using image editing software.

ImagePac

A widely used proprietary image file format developed by Kodak, designed specifically for storing photographic-quality images on CD.

image processing

Capturing and manipulating images to enhance or extract information.

image sensor

An electronic device capable of reacting to the impact of photons, converting them to an electrical current that is then passed on to the A-D converter. The most commonly image sensors used in digital imaging are CCD, CMD and CMOS.

indexed colour

Reduced colour mapping, 8 bit or less; done to reduce images to their smallest size. Commonly used for images placed on Internet pages. The 256-colour palette are also mapped for best results on the Internet, taking into account the differences between the Windows and Macintosh colour palettes.

inkjet printer

A type of printer that sprays dots of ink onto paper to create an image. Inkjet printers are normally inexpensive. Better-quality inkjet printers can attain near photo quality output.

interpolation

A process normally used in scanners and digital cameras to increase the image size in pixels by averaging the values of surrounding pixels.

Image and Scanner Interface Specification (ISIS)

An open standard, and accepted industry standard interface for image scanning technologies, developed in 1990, and currently supported by a number of application and scanner vendors.

ISO equivalency

The sensitivity rating for film or CCDs defined by the International Organization for Standardization (ISO). Digital cameras have fixed ISO equivalents or can be set to sensitivities ranging from 80 to 640 to achieve adequate exposure under different lighting conditions.

interface

A piece of hardware, a method, or a standard used for connection between or among computer devices.

J

Jaz drive

A computer disk drive made by Iomega that enables users to save about 1000 megabytes or 1 Gigabyte of information on their special disks.

JPEG

Joint Photographic Experts Group. Common format for displaying images on the Web. JFIF (JPEG File Interchange Format) is the actual file format used to compress an image with the JPEG method which is a standard developed for still-image compression sanctioned by the International Standards Organization (ISO).

jukebox

A peripheral device connected to a computer that can hold a number of optical disks or magnetic tapes at a time, making it possible to switch among them at will.

K

kilobyte (kB/KB)

A quantity of digital data. When referring to storage space or transmission rates for such data, the term (contracted to kB) refers to exactly one thousand (103) bytes. When referring to computer memory for such data, the term (contracted to KB) refers to the slightly larger, historic definition of 1,024 (210) bytes.
When referring an amount of computer memory, disk space, or document size consisting of approximately one thousand bytes: Actual value is 1024 bytes. Often used to refer to file sizes.

L

Lab colour

A colour model developed by the International Commission on Illumination (CIE). The Lab model, like other CIE colour models, defines colour values mathematically in a device-independent manner. Lab colour is consistent colour regardless of the device producing it.

laser printer

A printer using laser copier technology to produce high-quality printed material from computer data. The laser charges an electrostatically sensitive drum to accept carbon-based toners which are then transferred and fused to paper or transparency material.

LCD monitor

The liquid crystal display colour screen on most digital cameras, usually 1.8 to 2.5 inches measured diagonally; used to check images after they are shot. The LCD monitor is usually more accurate than an optical viewfinder, though not as convenient to use.

Linear Tape Open (LTO)

A magnetic tape data storage technology originally developed in the late 1990s as an open standards alternative to the proprietary magnetic tape formats.

lossless compression

A compression algorithm that reduces the storage space needed for an image file without real loss of data. The uncompressed image can be reconstructed to be identical to the original. Continuous-tone images will on the average be reduced to half the original size.

lossy compression

A compression algorithm that reduces file size by actually removing data from the image. The most effective lossy-compression algorithms work by discarding information that is not easily perceptible to the human eye. Effective compression ratios of 10:1 to 50:1 can be attained.

LZW

Lempel-Ziv-Welch is a proprietary lossless data-compression algorithm used in GIF and TIFF files.

M

macro lens

A digital camera lens mode that allows one to get very close to objects so that they appear greatly enlarged in the picture.

manual focus

Digital camera focus that can be manually be set at any point from near to far or in steps such as 3 feet, 15 feet, or infinity. Also provided as an override feature on some autofocus.

master image

A digital image, also referred to as a master image, that has been captured at the highest practicable quality or resolution and stored for long-term usage. Archival images are normally stored in an off-line mode on tape or CD and are accessed only for the production of surrogate or derivative images.

megabyte (MB)

A quantity of digital data. When referring to storage space or transmission rates for such data, the term refers to exactly one million (106) bytes. When referring to computer memory for such data, the term refers to the slightly larger, historic definition of 1,048,576 (220) bytes.

Megapixel (MP)

A quantity of digital data. When referring to storage space or transmission rates for such data, the term refers to exactly one million (106) bytes. When referring to computer memory for such data, the term refers to the slightly larger, historic definition of 1,048,576 (220) bytes.

memory

Commonly used to refer to a component in an electronic system that stores information for future use.

metadata

Data about data, or information known about the image in order to provide access to the image. Usually includes information about the intellectual content of the image, digital representation data, and security or rights management information.

migration

Preserving the integrity of digital images by transferring them across hardware and software configurations and across subsequent generations of computer technology as a means of preservation and access.

moiré

A visible pattern that occurs when one or more halftone screens are misregistered in a colour image.

multi-megapixel

The resolution of a digital camera with an image sensor capable of capturing two million pixels or more.

N

noise

Data or unidentifiable marks that may appear as bright specks in dark areas of a scan owing to electrical interference in the CCD sensor and associated circuitry.

O

OCR

Optical Character Recognition. The technology that allows computers to 'read' text from physical objects. OCR requires a graphical representation of text to interpret, which usually comes from a scanned image.

optical resolution

The true resolution of an image sensor based on the number of photosites on the surface of the image sensor without recourse to interpolation.

optical viewfinder

An optical glass device on the digital camera which, when looked through, shows the image to be photographed. The best digital cameras have both optical viewfinders and LCD monitors.

optical zoom

A zoom lens that uses movement of lens elements to achieve various fields of view. Regardless of whether the zoom is set for wide angle or telephoto viewing, the resolution of the image remains the same.

P

palette

The set of colours that appear in a particular digital image. Becomes part of a colour look-up table.

PCX

Image file format commonly used by IBM PC-compatible computers

photographic film

Substrate coated with emulsion containing light sensitive silver halide grains.

PhotoCD

Compact disc-type storage technology developed by Kodak. Five levels of image quality are stored for each image in an Imagepac on a Photo CD disc.

PhotoShop

PhotoShop is a widely used image editing application from Adobe, often used as a benchmark for other imaging applications.

photosite

A small area on the surface of an image sensor that captures the brightness for a single pixel in the image. There is one photosite for every pixel in the image.

PICT

A graphics file format widely used among Macintosh graphics and page-layout applications as an intermediary file format for transferring files between applications.

pixel

Short for picture element; the smallest unit that makes up an image. Each pixel can represent a number of different shades or colours, depending on how much storage space is allocated for it. Also used in measuring image size and resolution.

pixellation

Occurs when an image is enlarged (by zooming in) as each pixel in the image will take up two (or more) pixels on the display. This leads to the image having steps on edges that are anything other than horizontal or vertical. Also referred to as 'jaggies'.

PNG

Portable Network Graphics; a standard file format approved by the World Wide Web consortium to replace the gif file format. PNG is patent and license-free.

PostScript

A page description language developed by Adobe Systems, Inc. to control precisely how and where shapes and type will appear on a page. Software and hardware may be described as being PostScript compatible.

PPI

Pixels per inch; measurement used to describe the amount of detail within a digital image. An image that has a higher number of pixels per inch will show more detail than one which has fewer pixels per inch. The term is often conflated with dots per inch (DPI).

Q

quality assurance

Also referred to as quality control; the monitoring of systems and processes to ensure that the quality of work is within defined tolerances.

R

RAM

Random Access Memory

raster graphics

Also referred to as bitmap images; an image composed of pixels or an image represented with a matrix of dots.

RAW

A file format containing original data captured from an image sensor, usually of a digital camera. The RAW format saves all data obtained from the sensor, as well as metadata generated during the image capture process.

refreshing

Transferring digital data to new storage media to avoid the effects of media deterioration.

resampling

Changing the resolution of an image by increasing or decreasing the number of pixels.

resizing

To alter the resolution or the horizontal or vertical size of an image.

resolution

Spatial resolution, normally expressed as the number of pixels per linear unit e.g., 300 ppi (pixels per inch), sometimes dpi (dots per inch) or spi (samples per inch). For colour resolution see Bit Depth.

RGB

An additive colour model in which red, green and blue light is combined to create colours, combining full intensities of all three makes white. Digital cameras, scanners and monitors use RGB to record and display colours.

RLE

Run Length Encoding is a lossless compression format primarily used with Windows files (BMP, PCX). RLE supports only 256 colours.

ROM

Read Only Memory; memory that can be read but not updated or changed. Memory that is non-volatile and does not disappear when power is shut off. Commonly used in computers and CD formats such as CD-ROMs.

S

scan area

The maximum dimensions of the area in a flatbed scanner in which an original can be placed for scanning.

scanner

A device for capturing a digital image. There are many types of scanners, such as flatbed scanners, drum scanners, film scanners and microfilm scanners.

scanning area array

A hybrid of scanning linear array and area array used to describe the arrangement of the detector within a digital camera.

scanning linear array

A way in which the detector within a digital camera can be arranged resulting in high resolution images.

SCSI

Small Computer Serial Interface. A system of connecting a chain of computer peripherals to a computer.

Secure Digital (SD)

A memory card format for use in portable devices, such as mobile phones, digital cameras, GPS navigation devices, and tablet computers.

Secure Digital High Capacity (SDHC)

A high capacity memory card format for use in portable devices, defined in Version 2.0 of the SD specification. This format supports cards with capacities up to 32 Gigabytes.

serial port

A data transfer method used to connect a peripheral, such as a digital camera, to a computer. The serial connection will allow the peripheral to transfer data to the computer and vice versa.

sharpening

A software method of exaggerating edges in an image to give enhanced definition.

software

Written coded commands that tell a computer what tasks to perform. For example, Word, PhotoShop, Picture Easy, and PhotoDeluxe are software programs.

solid state drive (ssd)

A data storage device with no moving components, using only integrated circuits as memory to store data persistently.

spatial resolution

Describes how much detail in a photographic image is visible to the human eye. High-resolution images are sharp and more details are visible.

storage device

A device such as a magnetic disc, CD or tape used to store and retrieve digital files.

subtractive colours

The colour pigments cyan, magenta and yellow (CMY), which produce black when mixed in certain amounts. In printing, black is often added to give more definition, as mixing of actual inks cannot produce pure black.

surrogate image

A digital image derived from the archival Image. Usually not as high resolution as the archival image, surrogate images are usually used as output images on display devices or printers.

T

Terabyte (TB)

A quantity of digital data. When referring to digital storage space (it is almost exclusively used for this), the value means exactly one trillion (1012) bytes.

TFT-LCD

Thin film transistor liquid crystal display – a variant of a liquid crystal display, often used as a display on the back of digital cameras and other devices.

thumbnail image

Small, low-resolution preview image, often linked to a high-resolution version of the same image.

TIFF

Tagged Image File Format is an image file format used extensively for the storage of high-quality images.

transparent media adaptor

Part of a flatbed scanner used when scanning film or transparent media that allow light to pass through the media during the scanning process. Usually an optional extra.

true-colour image

A 24-bit image.

TWAIN

An acquire interface developed by a consortium of software developers as a standard for communications between scanners, imaging devices and now digital cameras and the computer software.

U

USB

Universal Serial Bus, a device allowing for easy connection of serial devices to PC. The aim of USB is to eliminate the serial port bottleneck that has plagued PCs since the beginning. Many newer peripheral devices such as digital cameras and scanners support USB.

V

vector graphic

An image composed of individual elements, e.g., arc, line, polygon, with their own attributes that can be individually edited. A drawing-type package is usually required to display such vector images.

W

watermark

Bits altered within an image to create a pattern that indicates proof of ownership. Unauthorized use of a watermarked image can then be traced.

white balance

How the colour white is reproduced. On a monitor the white point is the combination of all three red, green and blue phosphors at full intensity, as measured by its colour temperature in degrees K. It is used as a reference point in calibration.

WORM

Write Once; Read Many; refers to data storage that cannot be changed once written, though it may be read as many times.

X

Y

YCC

A colour encoding scheme developed by Kodak for its Imagepac file format.

Z

ZIP

A compression format. Files compressed with PKZip or WinZip are the most common archive format.

zip drive

A computer disk drive made by Iomega that enables users to save about one hundred megabytes of information on their special disks.

Questions you might ask

1. What is a digital image?
2. What can I use my digital images for?
3. Who will be able to use our digital images?
4. What is a pixel?
5. What does someone mean when they use the term 'bit depth'?
6. What are the benefits to my museum of a digitization project?
7. Will digitization help me manage my collection better?
8. What should I digitize first?
9. How much will digitization cost?
10. How can I reduce some of the costs of image digitization?
11. Are there grants available to help me buy computer equipment?
12. How can I develop a plan to manage a digitization project?
13. Is it best to use in-house staff and resources, or external contractors?
14. What kinds of staff and skills do you need for an image digitization project?
15. What kind of computer equipment will I need for my digitization project?
16. Should I buy a digital camera or a flat bed scanner?
17. What is the best file format for saving digital images in?
18. What is metadata?
19. What is the difference between a master image and a surrogate image?
20. Is it important to make back-up copies of my images?
21. What kind of storage device should I use to store my digital images?
22. If our museum owns an object, do we automatically own copyright of images of that object?
23. Once created can I simply crop and edit images however I like?
24. What is a "Rules of Use" statement and do I need one?

Image compression

An algorithm can be applied to a digital image file to compress it since a smaller file is easier to store and send. Compression techniques are distinguished by whether they remove detail and colour from the image. Lossless techniques compress image data without removing detail; lossy techniques compress image data by removing image detail.

Colour modes

Colour monitors, like televisions, use light in red (R), green (G), and blue (B) (RGB) to represent the entire spectrum of colour. In print, the four process pigment colours cyan (C), magenta (M), yellow (Y), and black (K) or (CMYK) are used for four-colour reproduction. These systems, or colour modes, are also referred to by the term "colour space"

Vector and bitmap formats

There are two basic forms of computer graphics, bitmaps and vector graphics: The kind you use determines the tools you choose. Bitmap formats, also known as raster graphics, are used in creating digital photographs, whereas vector formats are used primarily for drawings.

Data preservation

Protecting the integrity of a digital image must be a top priority for any digital preservation strategy. Preservation of images is an example of the ways in which content, defined in terms of structure and format, poses integrity problems for digital archives. It is difficult to plan a migration strategy, as it can be very difficult to anticipate the needs for migration, how much formatting will be required, and how much the process will cost. The process of migration can degrade data quality and this fact has implications for the integrity of the data.

Storage conditions

Storage conditions are an important factor in the preservation of certain types of storage media. Cooler and dryer storage conditions will extend life expectancy. Recommended conditions are a temperature between 10 and 20 degrees Centigrade and a relative humidity between 20 and 50 percent. Magnetic tape is the least stable medium owing to its inherent instability, which leads to chemical deterioration and physical wear from use. Optical disks can become unreadable because of warpage, corrosion or cracking in the reflective layer, and from dye deterioration or delamination.

The dangers of obsolescence

With technologies rapidly changing, electronic media are constantly becoming unreadable as new media and devices emerge and as the old disappear. Therefore data must be transferred to new media types and formats, as necessary. The purpose of migration is to preserve the integrity of digital objects and to retain the ability to retrieve, display and otherwise use.

Records should be migrated to new media and/or formats before the current format deteriorate or become obsolete. Both periodic inspections of storage media to identify any deterioration and continuing review of the evolution of the technology for signs of obsolescence are needed to determine when to migrate records.

This should be done for several reasons:

• Refreshing relates to preservation of the media; it is simply copying digital files from one storage device to another of the same type. Files should be migrated to new media before the current media deteriorate.
• Migration relates to the upgrade of the media to preserve the integrity of digital files and to retain the ability to retrieve them in the face of constantly changing technology. Files should be migrated to new media formats as the latter become viable and before current media become obsolete.
• Transformation relates to the translation of the current file formats to new file formats as they become viable. This may happen as a new standard becomes available or when current software becomes obsolete. If the files are in a proprietary format, problems may arise, as changes to the specifications of the file format may have been implemented by the format owner. In such cases, difficulty may be experienced when accessing the files.

Canadian rights

Copyright does not represent one right; it is a bundle of rights which includes the reproduction right that allows the copyright holder to authorize or preclude the reproduction of its copyright protected work. With certain exceptions, work protected by copyright can be reproduced only with the authorization of the copyright holder. When a work is being photographed using film and then digitized, it is being reproduced first when photographed, and next when that photograph is digitized. The photograph itself attracts copyright protection, and therefore copyright law has a layering effect. When the digitized images are subsequently compiled into a series of images, copyright may protect the image and the compilation as a whole, depending on a series of issues, discussed below.

Copyright also includes moral rights, which refer to the integrity of a work protected by copyright. The author of a work always holds the moral rights since they cannot be assigned. In Canada, however, moral rights can be waived. There are effectively three types of moral rights in Canada: the right to paternity, integrity of the work and the right of association. The right of paternity is the right to claim authorship or to remain anonymous or use a pseudonym regardless of the ownership of the copyright. The right of integrity prevents the mutilation or manipulation and perhaps even the destruction of a work that may be the author's prejudice regardless of whether the changes mentioned above are made to the original or a copy. The right of association allows the author to prevent the use of a work by another if such use runs contrary to the author's wishes, such as an association with a product, service, cause or institution.

It was held recently in an American case that compilations of images of artworks in the public domain could not be afforded copyright protection, since the digitized images lacked sufficient originality to meet the standards required by copyright law. The decision in Bridgeman Art Library Ltd. v Corel,^{Footnote 1} (Bridgeman), determined that the more faithful a reproduction of an artwork is to the original work, the less copyrightable it becomes, because such reproductions are not in and of themselves intellectual creations. The court made the analogy that a photograph of a two-dimensional artwork entirely faithful to the original was similar to a photocopy. It is understood that this decision will not be appealed. Although this decision is part of American case law, there is a small chance that it could be adopted in Canada, given certain similarities in our copyright laws, as explicitly recognized by the Federal Court of Canada in the Tele-Direct case, discussed below.

However, copyright lawyers in both the United States and Canada are now questioning the court's analogy between photographing a two-dimensional artwork in the public domain and photocopying it.

Whether a photographic reproduction of a painting in the public domain should be treated differently is debatable and can be determined only after a careful examination of the nature of creativity in photography. Therefore, it remains debatable to what extent the Bridgeman case is valid precedent.

At the time that this publication is being written, the breadth of copyright protection afforded to databases remains unclear. For current purposes, a database is a collection of data, text or images. As an example, a simple database could be the one listing members and their particulars, i.e., name, address, telephone number, etc. Other examples include databases of images of artworks or artefacts, research databases and internal collections management databases. The term "digitized images of works" refers to digitized images of works that may or may not be protected by copyright - bringing up the issue of whether the photographed version of an artwork is a new work protected by copyright. A recent decision of the Canadian Federal Court of Appeal, Tele-Direct Communications Inc. v American Business Information Inc. ^{Footnote 2} (Tele-Direct) held that databases that were compilations of factual information were not protected by copyright. It remains unclear in Canadian law what kinds of databases are protected by copyright, since many databases are compilations of factual information and not intellectual creations per se.

Exceptions to Copyright

Amendments to Canada's Copyright Act 4 in 1997 introduced specific exceptions to copyright for educational institutions and museums, archives, and libraries, which are exempted from copyright violation if they make a copy of a work in order to manage or maintain their respective collections or carry out limited interlibrary loans. Maintaining and managing a collection is defined by the legislation as making a copy of a work where:

• The original is rare or unpublished, deteriorating or lost, or is at risk of being damaged, deteriorating or lost,
• The original cannot be viewed or handled owing to its delicate state, and a copy is required for on-site consultation,
• The original is currently in an obsolete format, or the technology required to use the original is unavailable,
• The copy is required for internal recordkeeping and cataloguing,
• The copy is required for insurance purposes or police investigations, or
• The copy is necessary for restoration purposes.

Exceptions to copyright are also provided to educational institutions for use of works inside a classroom or as part of an examination. ^{Footnote 3} Museums, libraries, and archives that are part of educational institutions may avail themselves of all of the exceptions. Certain exceptions for all these groups apply only when a copy of the work in question is not "commercially available".

Only one limitation is placed on the exception: it cannot be used where an appropriate copy is commercially available in a medium and of a quality that is appropriate for the purposes outlined above. "Commercially available" includes copies available for licensing from a collective society. ^{Footnote 4}

Rights management and protection technologies

While images can also be protected and managed to some degree using current technologies, technology alone will not sufficiently protect digitized images. A combination of both legal and technology methods are required to protect digitized images from copyright infringement. Notwithstanding, even in combination, there are no guarantees that any image on the Internet is 100 percent protected, although an adequate combination of both legal and technology protections will provide a certain level of comfort. Finally, keep in mind that low-resolution thumbnail images are extremely difficult to reproduce because of their small scale.

While digital technologies create powerful new forms of preservation of text and images, and distribution of reproductions, at the same time they engender difficult problems involving intellectual property (IP) rights. It is becoming clear that amending and extending copyright legislation alone will not resolve this problem, if it can be resolved at all. For works distributed over networks, the model of licensing to end-users, as is done in the software industry, alleviates some problems, but will require a moderate approach on the part of owners, and an emphasis on the education of end-users.

Licensing, even if supported by registration, is seen as providing too little protection for aesthetic goods that retain their value over a long period. Hence, the issue of protection of digital images has attracted considerable attention, and a number of technologies, including watermarking, encryption, digital signatures, and fingerprinting, have been developed and are being marketed.

In their current implementations watermarks, signatures, and fingerprints primarily have value as deterrents to misuse and copyright infringement. Encryption can achieve high levels of security but even there the protection is never absolute and museums that implement such technologies must allow for ongoing infringements, usually at low levels with little economic consequences. On balance, the best strategy in the short term will be to keep the burden of protection technologies as light as possible within the legal requirements, and secure protection against economic loss through simple user licensing agreements constructed and enforced online for specific works and for specific times.

In the long run, what will count for users is ease of access, variety and comprehensiveness within a given domain. Since this is best achieved in a highly distributed, networked environment, there arises an acute need for computer systems that can manage "rights" - or more specifically, intellectual property (IP). A software technology on which such systems can be constructed is under active development and deployment, in the form of component software architectures. Examples are "Network OLE" (Microsoft), "CORBA" (Object Management Group) and "Java Beans" (Sun Microsystems). Out of the software components defined in these architectures, IP management systems (IPMS) build secure containers of encrypted content that contain the information and updating mechanisms the IPMS uses to enforce license terms, log usage, transmit royalty data to copyright collectives, and bill consumers.

How Scanners work

Most scanners work by reflecting a light source off the non-transparent object being scanned, such as a print, or by passing the light source through a transparency. A mirror and lens system focuses the light onto an image sensor, made up of a row of photosites, arranged in a row. As the image is scanned, a light source travels down the object. Some transparent and document scanners instead move the document past the light source. The image sensor turns the light source into pixels, which are combined to create the digital image.

Scanner types

The wide range of scanner types and models available can capture a variety of formats or objects.

A flatbed scanner, sometimes called a reflective scanner, is what most people first think of when they consider scanners; it is the most common and most versatile of all scanners on the market today. A flatbed scanner, which resembles a copying machine, can effectively scan any two-dimensional flat artwork, photographs, drawings, books, paper and near-flat three-dimensional objects.

Flatbed scanners can be adapted to scan film transparencies such as 35mm film by adding an optional transparent media adapter (TMA) unit that is usually mounted on top of the flatbed scanner in place of the standard cover. This device shines a bright light from above through the film to the image sensor below. The slides or negatives are then placed on the glass plate in an appropriate frame, illuminated from above, and scanned. Because of the small size of the originals, the resolution rendered by a flatbed scanner is usually lower than a film scanner, which results in a lower quality image. A dedicated film scanner would be a better option for scanning large numbers of 35mm slides or other transparencies.

A sheet fed scanner resembles a fax machine more than a copier, since it moves the page being scanned past the scanning head instead leaving the material stationary. Generally used for optical character recognition (OCR) or text scanning, they are not as exact as flatbed scanners because of the difficulty of moving a sheet of paper without introducing distortions. An option for the sheet fed scanner is an automatic sheet feeder to batch-process large quantities of paper.

A film scanner, most commonly referred to as a slide or transparency scanner, is specifically designed for scanning transparent film-based materials such as 35mm slides or negatives. Some of the higher end film scanners can also handle medium (4" x 5") or large-format film or transparencies. These scanners work by passing a light through the film rather than reflecting light off it. Because of their small size, slides need to be scanned at a very high resolution. Film scanners are generally more expensive than flatbed scanners and are less versatile. An option for the 35mm slide scanners is an automatic slide feeder for batch processing.

A combination scanner combines the transparency scanner and flatbed scanner in one unit. In addition to the usual glass plate for reflective objects, these scanners also have a separate built-in unit or drawer for inserting the film which can be scanned at high resolution.

Drum scanners are mainly used by scanning bureaus for high-quality professional layout scanning. The original image is mounted on a round cylinder or drum, which then spins around a central recording mechanism. With each pass the scan becomes more refined, resulting in a very-high-quality image. Drum scanners are very expensive, but offer features not available to desktop scanners, such as direct conversion to CMYK, auto sharpening, greater dynamic range, and large image scanning areas.

Handheld scanners, which come in a variety of shapes, capture images when the scanner is passed over the original material. They require a very steady hand to operate and tend to do a poor job in capturing colour. Although still the cheapest, they are rapidly being replaced by low-cost flatbed scanners. Handheld scanners should not be considered for capturing high quality images.

Video frame grabbers use a video camera or some other video signal, such as a VCR, to capture a video frame, then convert the video signal to a digital image using a special board inserted in the computer. Digital images converted from an analogue signal are of lower quality because of the limited quality of a video signal. A video camera can also be used to digitize frames containing three-dimensional objects.

Scanner quality

The quality of the scanner depends on its optical components and features, which in turn drive the cost of the scanner. You can perform tests or consult reviews done on scanners to compare the output quality. Some of the terms related to quality are:

Noise is electronic interference that can cause inaccuracies in images. In scanners, this noise has its greatest effect in low-light-level detection, i.e., when scanning the dark areas of images. Higher quality 30- or 36-bit scanners can give better results, as they tend to use higher quality (lower-noise) components.

Resolving power is a function not only of the optical resolution, but also the quality of the scanner's optical system, the stability of the transport mechanism, the type of sensing elements used, and other design factors. A high-quality scanner may have significantly more resolving power than a lower quality scanner of the same optical resolution.

Colour registration is the ability of the scanner's image sensor to precisely register the red, green and blue planes during the scan of a colour image, which is done at high speed. Proper alignment is necessary to produce clean colours.

Colour accuracy may vary between scanners. Different scanners may measure the same colour differently because of the spectral response of the image sensor, the nature of the light source used and the corrections applied by the scanning software.

Metadata

Many guidelines are available that you may wish to consult on information standards. These include the Categories for the Description of Works of Art, the Federated Guide to the Description of Architectural Drawings, Object ID, the Visual Resources Association Core Categories and others.

It is recommended that you use structured vocabularies, lexicons, and authority lists to describe the objects in your images. This is key to providing consistent access and retrieval of your images. The Art & Architecture Thesaurus and, is one example of a structured vocabulary that can help standardize the content of fields such as materials, technique, school/style, and object name/type in humanities databases. You may have created an authority list for use in your institution. You will also want to follow standards for information such as country codes and dates ISO 3166 and. It is important to be consistent in formatting your information.

Metadata about the image

You will need to create fields that describe the image itself. You will need to document what, if any, manipulation was done to an image, and describe the technical details of an image so that it can be interpreted by a system. This information is also necessary to assist in future technological reviews.

Types of digital cameras

Entry-level fixed-focus cameras. These cameras, designed for point-and-shoot applications, have long battery life and are generally highly portable; making them extremely convenient. While the resolution and colour depth of these cameras consistently improves, they are often limited by their small lenses and rudimentary user controls. They may however, be useable by small museums conducting digitization projects on a budget; such cameras should have at a minimum: manual override features (control of shutter speed, elimination of flash, optical zoom, etc.), 12 megapixel resolution (this varies with the desired size of your final image), and the ability to produce 24-bit RAW (lossless) images.

Mid-level Digital Single Lens Reflex (DSLR) cameras. These cameras are based on traditional 35mm film models, and include similar features and functions such as exchangeable lenses, through-the-lens focussing, overrides of manual controls, and a choice of exposure modes such as aperture-priority or shutter-priority. These cameras appeal to photographers who like to have creative control of their camera settings; they produce prints that typically approach or equal the resolution and colour depth producible by traditional 35mm film; which is generally considered to be under optimal situations 24-bits colour depth, and 24 megapixel resolution (or greater – there is much debate), and under typical situations (with no tripod) 24-bit colour depth and 12 megapixel resolution. Such cameras tend to be the most suitable for collections digitization projects.

High-end professional cameras. These DSLR cameras are used to capture images at very high quality (vista photography, or wall-sized prints), exceeding a level of detail produced by 35mm film. As these cameras offer no advantage over mid-level SLR equipment in the context of artefact digitization, they are generally not considered due to their higher price point. This may change as the cost of sensors decreases, opening up the possibility of using any stored artefact image for unforeseen large format applications.

The camera's "front end"

In terms of gathering and focusing light, analogue and digital cameras are nearly identical. Both must let in the proper amount of light for the proper time, and then focus it, an operation that requires a carefully coordinated combination of the following features:

Camera functions

Some or all of these functions may be fully automatic in some digital cameras, much like film cameras. However, professional digital cameras are designed to allow for manual adjustments to shutter speed, aperture and focus.

Preparing a setting

Lighting is a key ingredient in the mood of a photograph. It is important to analyze the whole scene surrounding the subject before clicking the shutter. This is the skill of a good photographer: monitoring of the subject's placement within the context of a larger scene. A studio is an area in which to take photographs under controlled conditions.

In many cases, objects may fit on a table top for photography, which requires only minimum background. The same principles can be applied to larger items as well. For complete control, one must exclude all light sources not controllable by the photographer. The area selected should be big enough so that the intended objects can be photographed without resorting to wide-angle lenses. You can eliminate most distracting information using a plain background. To set up a makeshift studio you will need to consider a number of items. Backgrounds can be as simple as a blank white wall, which can be made to appear any shade or colour by controlling white or coloured light falling on it. Rolls of paper can also be taped high on the wall and rolled out across the table.

Besides a camera, a sturdy tripod and lights; various props for supporting objects, reflector cards, and modelling clay, (along with tweezers, brushes, clean white cotton gloves, pins, and string) may be used in the studio.

Getting the lighting right

As mentioned earlier, photography is simply time and light and the basic components of light are direction and quality. Direction gives shape and emphasis to the subject: the quality refers to the harshness or softness of the light, regardless of direction. These components can be seen outdoors as the direction of the sun and whether it is direct hard sunlight or softer light diffused by clouds.

To the human eye, the most natural lighting is a reflection of what we observe outdoors, where the sun's illumination comes from above the camera-to-subject axis. Observing these natural rules, although they can be broken for certain special effects, gives a subconscious reassuring sense of realism to the illumination of an object in a photo.

A simple lighting setup might use one light to illuminate the subject from one side. To add a more natural look, a reflector can be placed on the opposite side to bounce light back into the shadows created by the light source. The angle of the light can be adjusted to vary the shape of the subject; the harshness or softness can also be varied to suit the eye.

Having a soft light source does not necessarily reduce the need for a reflector. Although the eye may see detail in the shadows, film is unfortunately more limited in its ability to record large differences between highlights and shadows. Scenes or sets need to be illuminated at a lower contrast to offset the increase in contrast that occurs during processing.

For reflective objects such as coins or other metallic surfaces, follow the line of view from the camera lens to the object, then again as it is reflected away at an equal angle relative to the perpendicular. Placing a reflector or light source at this position will cause it to reflect off the subject directly back into the lens. This will lighten the tones of the metallic surface and bring up its texture as well.

Film

The choice of materials can affect the overall quality of the image. Films vary not only in speed but also in colour rendition; resolution (slower film speeds tend to equal higher resolution); colour balance (optimized for different colour temperatures); exposure latitude, and so on. It almost goes without saying that the film should give accurate colours and good resolution, and be balanced for your lighting conditions.

The most important choices to be made here concern the film format, and there are occasions when the wealth of detail in the subject means that a larger format is needed (e.g. for large paintings or architectural detail over a large area).

Lenses

Image quality can vary enormously depending on the quality of the lens(es) used -- try not to compromise here. Avoid zoom lenses if at all possible -- a good prime lens (i.e., not a zoom) generally offers noticeably higher quality images. Similarly, if there is a reasonable amount of macro (close-up) work to be undertaken, invest in a dedicated macro lens rather than one that offers this capability as an added feature.

Colour targets

Colour targets can serve as checks on the photography, provide measurements for the transparency scanning, calibrate monitors and printers, and facilitate visual evaluation of on-screen and printed versions of the digital images. Both grey scale and colour targets can be included during photography to provide a level of control over colour and tone shifts: The colour-control bars help the photographer and scanner operator compare the colour of the subject with known printing colours. The grey scale is a quality-control device of stepped, neutral values. Both colour and grey scale targets are used in colour-matching images during photography, digitization, on-screen viewing, and printing. Good colour-matching requires not only the information on the colour scale, but also the grey-scale control of shadows, mid-tones and highlights.

Film processing

For the film development process, find a reliable photo lab that has experience with developing large quantities of high-quality images. The first step is to initiate a dialogue with the film processor to explain your needs. Do not expect high-quality production on a rush basis; explain that you are looking for consistent results. For best and most uniform results use the following: Standard background and proper exposure; a manual override or fixed setting, so that all images are consistent in colour and exposure; and a consistent film stock to make printing and digitization easier.

Inkjet Printers

Inkjet printers use the "non-impact" principle of spraying tiny accurately aimed bits of ink on to paper. The ink, in a tiny reservoir behind each nozzle, is heated which forces the tiny drop through the nozzle. A variation of the thermal method is the piezo-electric system in which each nozzle is connected to a so-called piezo crystal, which forces a tiny drop of ink out of the nozzle when it reacts to an electrical charge.

Inkjet printers can produce very-high-quality images, and initial purchase prices are low. On the down side, print times, while constantly improving, are still slow relative to laser printers. Nevertheless, inkjet printers produce photographic-quality images much faster and at much lower cost than traditional photographs.

Laser Printers

Laser printing works by breaking an image down into a bitmap or a series of tiny squares. Next, the laser sweeps across a charged photoreceptor known as a "drum", sending a beam of light, leaving a positive electric charge which creates a mirror image of the original document on the drum. Colour is printed as a separate images or layers by mixing magenta, then cyan, then yellow, and finally black. The image is then transferred onto paper by applying negative charge that attracts the toner to the drum. The image is transferred to the paper when it comes in contact with the drum and, finally, heat and pressure are applied to the paper. This melts the toner, which contains small amounts of wax, and fixes it to the paper.

Laser printers are popular with businesses, where speed and lower per-print costs are important. However, high initial costs and less than perfect images make laser printers less attractive to most digital photographers.

Dye-Sublimation Printers

Designed for professional graphic artists, dye-sublimation printers operate like inkjet printers, except that they reach such high temperatures (upwards of 500 degrees Celsius) that allows colours to mix extremely well. Each colour--usually yellow, cyan, magenta and black--is printed individually, then mixed seamlessly on the paper.

This technique produces the highest quality images, making it ideal for professional graphic artists and photographers. However, the printers themselves are very expensive, costing ten or twenty times as much as inkjet printers. In addition, they require paper that is specially coated to receive the ink without bleeding, which poses an additional cost.

Thermal Wax Printers

Closely resembling the dye-sublimation method, thermal wax printers are designed especially to produce colour transparencies. The inks are wax-based, enabling them to adhere to the special transparency paper required.

These printers are designed for producing transparencies, but they don't necessarily work for all-purpose colour printing as the level of detail they can capture is limited unless you will be creating transparencies from digital images. They are also expensive to buy, and materials can be expensive.

Thermo-autochrome

Thermo-autochrome printing is most like traditional photographic processing. Thermo-autochrome paper is covered with three hidden layers of light-sensitive ink--cyan, magenta and yellow--each of which is activated at a certain temperature. As the special paper passes through the printer, tiny modules heat up tiny areas of the paper, activating the hidden colours one by one. Then an ultraviolet light passes across the paper, "fixing" the colours--that is, preventing the inactivated ink from developing.

The thermo-autochrome method is designed especially for digital photography. However, the printer has very limited use, since it can only use highly specialized paper.

Tips for printing digital images

• Choose the right paper. The plain paper used for printing documents is useful for many applications, but for high-quality image work, it will not provide optimal results, since it allows colours to bleed. Select a high-quality paper designed to provide vibrant colours and image stability during inkjet printing. Coated and photographic papers are more expensive, but offer far better quality. Consider how you intend to use these papers.
• Don't blow up images to fit a full page. Most images look better left at snapshot size.
• Use the recommended printer driver settings that were installed with the printer.
• Handle the paper in the right way, as the instructions indicate. For example, you should not touch the receiver layer of photographic paper.