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Guides to Quality in Visual Resource Imaging

1. Planning an Imaging Project
Linda Serenson Colet
© 2000 Council on Library and Information Resources


1.0 Introduction
2.0 Articulating Project Scope and Goals
2.1 Institutional and Departmental Uses for Digital Imaging
2.2 Identifying the Type of Material
2.3 Digital Imaging Uses (Functional Requirements)
2.4 Digital Imaging Uses (Calculating File Size)
2.5 Budget Considerations
3.0 Analyzing Characteristics and Conditions of the Source Images
3.1 Estimating the Number of Images to be Captured
3.2 Source Formats: Film Intermediaries Versus Original Sources
3.3 Size of the Source Originals
3.4 Unusual Characteristics and Features
3.5 Condition and Disposition of Originals
4.0 Developing Appropriate Capture Specifications and Processes
4.1 Image-Capture Specifications
4.2 Testing and Evaluation
4.3 Efficient Workflow
4.4 Documenting the Decision-Making Process
5.0 Conclusion

1.0 Introduction

This guide is intended to serve as a guide to planning a digital imaging project. It encompasses the digitizing of two-dimensional artwork, such as original photographs, prints, drawings, and glass-plate negatives; library materials such as maps; and other visual resources. The document will help project managers in museums, libraries, universities, and archives gain a comprehensive understanding of the issues related to creating a high-quality digital archive for access or preservation, or both. It analyzes the tasks involved in choosing a method for capturing the original source material and the decisions associated with developing the digital archive to serve a wide range of uses and users. Planning for such uses as the Web, collections-management systems, educational kiosks, and high-end book publications is also discussed. The message stressed throughout the guide is that one should digitize at the highest level of quality affordable. This minimizes the need to re-digitize (Frey and Süsstrunk 1996; Frey and Süsstrunk 1999), saves the original source material from excessive handling, and prolongs the usefulness of the digital archive.

Although comprehensive in scope, the guide does not cover designing the software applications that will use the digital images. Likewise, it does not cover how to develop the content and cataloging features that go along with the digital images. It does not address copyright issues relating to the use of the images. The guide focuses on the tasks necessary to produce digital images for an enduring, high-quality archive and the decision processes that accompany these tasks.

Several issues must be addressed in planning a digital project. How does one decide upon the initial scope of the project and its immediate and long-term goals? Answering these questions involves identifying institutional needs and the type of original material to digitize, deciding whether the image is being created for a use-specific project or a use-neutral archive, and assessing the budget.

Evaluating the characteristics of the source materials to be digitized is part of the planning process. This involves determining the number of images to be digitized, identifying whether the source format is film intermediaries or original materials, considering the size of the materials to be digitized, assessing any unusual characteristics of the source material, and reviewing the condition and disposition of originals.

The scope of the project and the characteristics of the source materials translate into image-capture specifications and procedures for building a collection of digital images. The project should be planned to progress efficiently and the workflow should be well ordered. Digital equipment must be chosen to optimize quality and level of production, the appropriate hardware and software must be selected, and image capture and editing rules must be set to maximize efficiency. Appropriate procedures must be set for handling and storing materials, and the decision-making process should be documented by metadata and workflow logs.

2.0 Articulating Project Scope and Goals

A great deal of planning is necessary to produce an enduring, high-quality, digital archive. Digital technology, archival methods, and budget options need to be explored (Library of Congress, National Digital Library Program 1997). Before a single digital image is produced, the project manager should perform a thorough needs analysis. Such an analysis entails identifying institutional priorities, determining potential users and uses of the digital images, and allocating financial resources. The analysis should include decisions about whether the project can be done within one's institution, outsourced to a vendor, or accomplished through a hybrid approach. A thorough needs analysis will help the manager make good decisions throughout the project and accommodate inevitable shifts in priorities and requirements. The details of a needs analysis are as follows.

2.1 Institutional and Departmental Uses for Digital Imaging

Defining institutional priorities involves evaluating the goals of the institution as well as the needs of various departments within that institution (Carpenter, Serenson Colet, Keller, and Landsberg 1997-1998). If a manager can identify institutional priorities and align the digitization project with them, the digital initiative will have a greater likelihood of long-term success.

One of the most important questions to ask is how a digital initiative can support the institutional priorities. For example, upper management may perceive digital imaging as a priority because they believe it offers a promising way to improve access, which will support an institution's goal of attracting more visitors.

Such was the case at the Library of Congress (LC), where the American Memory Project answered an institutional need to create new paradigms for access to library resources. In the past, visitors had to go to the LC to use its resources. Managers recognized that the Library's vast store of information could be used more broadly if it were available online (Campbell 1999). Providing online access to the Library's visual materials was consistent with management's goal of expanding the library's resources through new means of access and represented a powerful way to distribute information.

Management may also view digital imaging as a way to improve internal processes, such as the sharing of visual information. For example, online visual tools for collections and exhibitions management can help centralize standard forms and checklists used across departments. Centralization avoids redundancy of processes and reduces unwanted inconsistencies and discrepancies in information.

The Ratti Textile Center at the Metropolitan Museum of Art in New York City began a digital initiative to create images that would provide greater access to the public. Coupled with a new collections-management system, the digital project served both public needs and institutional priorities. Today, the museum's photographic services department maintains an impressive digital operation that supports both archival and collections-management functions throughout the institution.

It is also important to consider how the digital initiative can support the activities of specific departments and projects within the institution (e.g., Web initiatives, the development of collections-management systems, graphics, and publications). By identifying the departments that can most benefit from digital imaging, a manager may find a good justification for starting the digital project as a short-term pilot project that can eventually lead to a broader, longer-term initiative.

Managers may also want to consider factors that could restrict a project, such as a lack of staff resources, a lukewarm or negative response to technology, copyright law, and budget. By speaking to other managers within an institution, a manager can learn what projects succeeded or failed and why.

2.2 Identifying the Type of Material

The nature of the institution typically determines the type of material to be digitized and the conditions for its handling. Two-dimensional visual materials, such as photographs, prints, drawings, and maps, all have special requirements for handling and digitizing. Identifying these requirements is an important step in planning a digital strategy. Section 3 addresses in depth the analysis of the characteristics and condition of the source material.

2.3 Digital Imaging Uses (Functional Requirements)

It is important to consider the purposes for which users will access the digital images. Will they use the images for on-screen browsing or for reference and detailed study? Will they want to download images for classroom projection?

The answers to these questions affect the technology requirements and equipment specifications. The requirements for on-screen display must be considered. Another consideration is whether one should expect to be able to accommodate as-yet-unknown users who wish to access images for reasons not yet evident. In seeking answers to such questions, it is useful to review important user studies (e.g., the MESL Project, AMICO).1

In considering the possible uses and users of the digitized material, it helps to identify the project's scope. Is it a specific access project (e.g., building a Web site) or one that supports multiple applications?

A use-specific initiative is designed with a particular goal and with specific users and uses in mind. The goals are usually limited to improving access to source content, rather than encompassing archival and conservation goals. A use-specific initiative often focuses on the immediate purpose for which the images will be used; the images may be limited in their use for other purposes. For example, images that are digitized for posting on a Web page to be viewed by casual users may not be appropriate for research or book and catalog publication, which typically require high-quality capture.

After a specific use has been defined, specifications can be developed for digital capture and access. A single standard may be set for how the images will be digitized (e.g., resolution file size and cropping conditions). For example, if the images to be digitized will be used only in a collections-management system and will therefore be treated only as data elements within a database, one can specify a low-resolution file size, crop proportions appropriate to the application used, and make contrast adjustments that are favorable for on-screen resolution.

A disadvantage of use-specific projects is that the resulting images might not be appropriate for other uses, should the need arise. If the limitations of a use-specific project are not clear to management, then expanding the scope of the project to support other uses can be problematic. It can be difficult to ask management to commit the necessary funds and resources for additional purposes (e.g., to support scholarly research as well as casual viewing). A better solution, therefore, is a use-neutral approach. With this approach, an image is digitized once, at the highest level of quality affordable, and studio standards such as color matching and contrast levels are set so that the image can be used for multiple applications (Frey and Süsstrunk 1999). The advantage to this approach is that the digital images can then be used for access projects (Web sites and collections-management systems) as well as more demanding applications. The digital archive can also support the potential uses of a general audience.

The use-neutral approach requires consistency in how the images are digitized, a focus on quality control of the images, the monitoring of color management and migration, and a consideration of storage and system-integration needs. This comprehensive approach is challenging, but the benefits are far greater than those associated with a use-specific approach. With a use-neutral approach, there is a better chance that one will not have to re-digitize for a long time, and this will protect the original from excessive handling. In addition, one does not have to repeat the digitizing project each time a different use occurs for the digital archive.

The Museum of Modern Art (MoMA) in New York City is employing a use-neutral approach to archive its collection of original photographs at high resolution (70-100 MB files). It is then using the digital reproductions to serve in multiple projects, including high-end publications, scholarly kiosks, collections and exhibitions-management systems, Web sites, and other applications (Serenson Colet, Keller, and Landsberg 1997-1998). The Museum has published four books using direct digital files. They are the exhibition catalog Aleksandr Rodchenko: Russian Revolutionary Modernist (1998), a reprint of Looking at Photographs: 100 Pictures from the Collection of The Museum of Modern Art (1999), a volume of Nicholas Nixon photographs: The Brown Sisters (1999), and the exhibition catalog Walker Evans & Company (2000).2

The goal of the use-neutral approach is to digitize images at high resolution and with neutral standards. Digitizing an image with neutral standards means that minimal image editing is done to the archival copy in the areas of color, contrast, sharpening, and cropping. After the image is pulled from the archive to be used for a particular application, it is then optimized for that application.

The use-neutral approach may support the long-term success of a project and secure its future because the institution has a vested interest in amassing and maintaining digital collections that can support the use of images in Web sites, public access kiosks, and high-quality publications. Developing a long-term archive can, in the end, be more cost-effective and safer for the works.

The disadvantage of a use-neutral approach is that it requires a tremendous investment of time and money to develop in-house knowledge of how digital technology works and the standards that go along with it. One must thoroughly assess institutional imaging standards and compatibility issues in terms of file size, image editing decisions, and intranet viability for transferring derivative images of the master image. As Mikki Carpenter, director of photographic services and permissions at MoMA, has stated:

"Every professional in your institution who is responsible for publications, publicity, graphic design, product design, and production will use the digital images . . . It is imperative that [their] concerns . . . be addressed before you start image capture . . . enlist your professional counter-parts in this process even before you begin. Their concerns and issues will be crucial in guiding your research and shaping your ultimate decisions." (Carpenter, Serenson Colet, Keller, and Landsberg 1997-1998).

A use-neutral effort can be successful only with full management support and cooperation among a variety of departments. A careful analysis of both the institutional and departmental priorities is essential to succeed with the use-neutral approach.

Using digitized images online raises the question of whether the image can fully serve as a substitute for the original. This has implications for preservation. Use-neutral projects generally address issues of preservation in more detail than do use-specific initiatives (unless, of course, the use-specific initiative is one devoted to preservation). Can and should the digital surrogate serve as a preservation copy or a facsimile when the original no longer exists? Preservationists need to consider whether microfiche will accompany the digital image as a second preservation copy. Libraries with brittle books and maps often face these issues of preservation and access when developing the goals for their digital projects.

For example, Columbia's Oversized Color Image Project addressed a methodology for dealing with this preservation issue (Gertz 1995 and Gertz 1996, as noted by the Image Quality Working Group 1997). Preservationists at Columbia (Cartolano, Gertz, and Klimley 1997) concluded that microfiche should be used as the preservation copy and the digital surrogates should be used for access (both electronically and in print). The digital surrogates included both a master archival digital copy and a microfiche copy. In a more recent study, Chapman, Conway, and Kenney (1999) confirmed the value of using microfilm as the preservation medium in conjunction with the digital image. It is important to note that concerns about using the digital image as a preservation copy may change as color-imaging standards improve and strategies for migration become better established.3

The Columbia example also illustrates how the needs of users were explicitly considered. The project invited potential users to evaluate the online accessibility of images in both electronic and print versions.

2.4 Digital Imaging Uses (Calculating File Size)

When it is time to retrieve an image from the archive for a specific use, one must determine what file size is required. Determining the resolution needed for a specific use depends on the characteristics of the archived collection and how the image will be used.

Guidelines for calculating file size are provided by Richard Benson, of Yale University; Bob Hennessy, photographer and printer; and Sabine Süsstrunk, of the Swiss Federal Institute of Technology. Additional information on determining the file size required for specific uses may be found in Frey and Reilly (1999).

Pixel dimensions x number of channels = file size
Example: 4,300 x 5,300 pixels x 3 channels = 68,370,000 bytes = approximately 69 MB

OR

Dimensions in inches x resolution per inch x number of channels = file size

Example: 8 inches by 10 inches at 300 ppi, 3 channels:
8 x 300 x 10 x 300 x 3 = approximately 22 MB

Note: When referring to resolution per inch, multiply each dimension by the resolution to obtain the total number of pixels required for a specific application.

Ppi, dpi, and lpi are all abbreviations used to describe resolution. They may be defined as follows:

The number of channels is determined as follows:

(We assume that 8 bits = 1 byte = 256 levels per channel. However, some archiving applications might require storing data of up to 16 bits [2 bytes] per channel).

2.5 Budget Considerations

It is always a challenge to secure funds to initiate a project and to manage it on an ongoing basis. Institutions fortunate enough to obtain funding are usually working with a schedule and typically must reach certain milestones before further funding is provided. Even if sustained funding is uncertain, it is best to budget long-term to estimate ongoing expenses (Carpenter and Serenson Colet 1998). It is also important to have milestones that are flexible enough to accommodate unforeseen developments.

2.5.1 In-house Staffing, Outsourcing, or a Hybrid Approach

Ensuring a cost-effective and efficient project requires committing resources, developing expertise in digitizing and archiving, and creating a production workflow that balances quality with the rate of production. Institutions generally have three options: using in-house staff, contracting with an outside vendor, or using a combination of the two (the hybrid approach). There is no easy answer about which is the best method, and the costs will vary widely, depending on the institution, the vendor(s), and the nature of the project. A formal cost analysis will be necessary to determine how to proceed. The following are some general issues to consider.

Outside vendor services are often available to capture digital images and process them onto storage media. Services may include advice on digitizing and production strategies, color correction, and the management of digital metadata. (Metadata is data about data, such as documentation about the type of digital capture, equipment settings, and image-editing rules used to create the digital image). An institution may also choose to use outside services to manage enterprise-wide solutions for archival storage, system integration, backup, and network access. This is often the case for institutions whose information systems departments do not have sufficient resources to support the digital project. The costs for external vendor services range widely, from $2 to $50 per image, or more.

Management must also determine whether an outside service is the most efficient solution for their institution. Outside services can be an efficient solution, even if they are expensive, for an institution that does not find it feasible to develop internal expertise in digitizing and archiving because the project has a short life span and a rapidly approaching completion date. Vendors can often start a project quickly because they already have the needed expertise and do not have to spend time in research and development.

As a project continues, the efficiency of relying on the services of an outside vendor will diminish. An organization that does not develop any internal digital knowledge will be forced to rely more and more on the vendor as the project grows. Costs will also rise. Reliance on a vendor requires the institution to relinquish control over technical decisions, making it difficult for the institution to determine whether the costs are justified. Reliance on a vendor also means that an institution may not learn how to manage the intricacies of digital imaging as they affect archival decisions and preservation strategies. The institution is responsible for these issues over time, and there is no guarantee that the vendor will be available to address problems with archiving should they arise.

An alternative to relying on an external vendor is to use internal staff and resources to digitize the images, process them onto storage media, and manage the workflow and archival process. Since planning and executing digital projects have become integral parts of museum management, some institutions have decided that developing the knowledge in-house is more cost-effective in the end. An investment in developing staff expertise allows one to service not only the current digital project but also other digital initiatives throughout the institution. It allows staff to participate in technical decisions that affect the quality of the digitizing process as well as in discussions of archival and preservation issues. Such decisions about technical, archival, and preservation issues will affect how users access institutional collections over time.

If work is done internally, additional resources and funding will be required to

Although potentially rewarding in terms of knowledge gained, implementing a digital project using in-house resources can be problematic if the costs are not properly managed. One must be wary of spending too much time and money on any single aspect to the detriment of others. For example, if an institution spends too much time evaluating equipment or bringing in consultants, it may not have enough funds to get the project off the ground. Without upper management's conviction that a project has long-range advantages for the institution as a whole, the project can come to a halt, despite favorable evaluation results. In-house projects can also fail when there is a lack of expertise on particular aspects and an unwillingness to hire consultants to provide such expertise and to educate staff. In particular, staff may initially lack skills in color-management issues, technical systems integration, and production quotas.

An alternative to outsourcing or using internal staff is the hybrid approach. Implemented properly, this approach combines the strengths of both internal and external resources in a synergistic way. The following three scenarios provide some examples of how labor can be divided:

The approach that is selected (in-house, outsource, or hybrid) will have a direct effect on staffing and equipment decisions and, therefore, on the budget. Table 1 helps identify the staffing and equipment implications of in-house and outsourcing approaches. Elements of each approach may be combined. Actual costs are not identified because they will vary according to an institution's geographic area, staff experience, and skill level.

All the staffing and equipment items noted in Table 1 are important. Cutting back on any of them will have negative implications on a project. (Refer to the section entitled "Managing Cost Implications" for further details.)

Table 1. Planning a digital imaging project: staffing and equipment guidelines

Staffing Description
In-house   project
Outsourced project
Project managers (internal) Internal project managers are required to manage project goals and institutional expectations, identify staffing and equipment costs, coordinate archival and access needs across departments, and adapt the digital plan as necessary to achieve success. x x
Vendor project managers Vendor project managers run the digital operation and allocate appropriate staffing and expertise to the project.   x
Photo services staff Institutions with an internal photo services division should use it to manage, operate, and maintain the digital project. If the project is outsourced, photo services staff must closely interact with the vendor. x x
Curatorial and archives staff Internal curatorial or archives staff members, or both, identify project goals, choose objects for digitizing, identify preservation concerns, and project the short- and long-term uses for the digital images. x x
Conservators and preservationists In-house conservators or preservationists should review the project before it begins and identify conservation and preservation concerns. x x
External consultants External consultants may advise on digital studio setup, system integration and networking concerns, archival storage issues, color-management needs, and other matters. x x
Grant writers Grant writers may be needed to write proposals to secure funding for the project. x x
Computer/technology staff Computer and technology staff set up the system, resolve network issues, design storage systems, and performs similar tasks. An institution that does not have these resources must secure outside resources to set up the computers and networks and to handle maintenance. x x
Preparators and art handlers Preparators and art handlers prepare and transport objects to the studio for digitizing. An institution dealing with surrogates may not require this type of staff. x x
Quality and production managers These supervisors set and maintain image quality-control standards and production goals. Their functions should be separate from those of the scanner or camera operators and technicians. x  
Scanner or camera operators and technicians Scanner or camera operators and technicians capture and edit the original object or surrogate. x  
Post-processors Once a digital image has been captured, it is passed to a post-processor, who processes it on archival storage mediums and prepares it for short- and long-term use. x  
Administrative assistants Assistants create and maintain archival logs and keep track of the metadata information to ensure that the digital process is documented and that the documentation can be searched for easy retrieval. x x
Vendor services for digital capture, post-processing, and administering logs Significant vendor costs will be incurred for digital capture, post-processing, administering logs, and equipment use. Often this cost is subsumed in the per-image cost.   x
Equipment      
Digital evaluation costs Before the project begins, one has the option of renting digital equipment (e.g., digital camera backs, flatbed scanners, and lighting) for testing and evaluation or setting up tests at the outside vendor location. Note: Some institutions may decide not to test as this can be expensive and time-consuming. x x
Digital capture equipment Equipment must be purchased to digitally capture the original object or surrogate. x  
Copystand or cradle or flatbed scanner If using a digital camera back (attached to a traditional camera), one needs a customized copystand or cradle to hold the object being captured. A flatbed scanner must be set up properly or customized for the project. x  
Computer equipment and server setups Image processing computers capable of high-volume data throughput are the backbone to the digital capture, post-processing, and editing stations. They are also needed for the administrative stations, and to review and check image quality, keep metadata logs, and retrieve images from the archive. In addition, servers are needed for networking the computers within and outside the studio. The number of computers required depends on whether this done in-house or is outsourced. x x
Lighting The appropriate lighting for digital capture (e.g., halogen, HMI, strobe) must be chosen. x  
Voltage regulators Voltage regulators are required to control fluctuations in scanning caused by lighting or electrical jumps. x  
Lightbox A lightbox is used to view and compare originals or surrogates with the digital images. x x
Conservation items for the studio Conservation items include air filters, air conditioners, white gloves, and lab coats. x  
Color management controls Tools for controlling color management in the studio include targets, gray-scale and color bars, densitometers, calibration equipment, and profiles. x x
Post-processing equipment Post-processing equipment includes tape drives and CD burners. x  
Archival storage mediums Equipment used to archive the digital images includes CDs, tapes, and near-line network storage. x x
Transfer mediums Equipment such as ZIP, JAZ, and intranet or Internet connections is needed to transfer images outside the studio. x x
General supplies for digital capture General supplies include extra light bulbs, storage disks, and office materials. x  

Regardless of whether the work is done in-house or is outsourced, a significant number of in-house staff members are required to manage the project. In addition, over time, the cost of vendor project management and outsourced digital capture and post-processing services can equal or exceed costs of an in-house project.

Many of the costs noted in Table 1 will be incurred at the beginning of the project. Once the project is under way, most of the expenses are for maintenance and support to sustain the operation. Digitizing is labor-intensive, and a project involving a large quantity of materials (thousands or millions of objects) can take years to complete. Ongoing maintenance may include the following:

2.5.2 Managing Cost Implications

Because funds are finite, it is useful to ask whether compromises can be made in any area. The answer depends on the details associated with the project's scope, its intent, and the nature of the source originals. It is important to be informed about the consequences of cutting costs in various ways and to be aware of the costs associated with every aspect of the imaging process.

Although the expenses for digital projects may seem overwhelming, there are serious implications to cutting corners. A decision to reduce spending in one area can adversely affect other aspects of the project. For example, if an extra staff person or extra computer is cut, production will be slowed, other things being equal, and this will cost money in the end. Although cutting costs may appear to be a straightforward task that is based on a cost-benefit analysis, it could be difficult to calculate long-term revenue "lost." Managers should have several projected scenarios of long-term revenue figures; this will enable them to consider the consequences of cutting costs on the basis of alternative assumptions.

If one cannot afford all the costs up front, it will be necessary to determine how many images can be digitized per year without sacrificing quality and then to designate a longer period to complete the project. It is better to set modest goals than to create unrealistic expectations. Unforeseen expenses are inevitable and may occur as early as the first three months of production. They must be borne in mind when projecting how long it will take to digitize the source material and the costs associated with that length of time. Often, if a projection is evaluated during the stages of testing and evaluation, the project manager will have a general idea of how best to budget for a project. Spreading out the cost over several years can often fit nicely into a funding proposal.

2.5.2.1 Quality versus quantity
A common issue in managing the finances of a digital project is how to achieve the proper balance between quality and rate of production. Cutting corners in quality creates the risk of having to re-digitize some images, and this risk should be minimized. It is always preferable to reach a well-defined and objective measure of affordable quality, as defined not only in terms of image resolution but also in terms other metrics. The whole image processing chain has to be examined. Besides issues concerning the system for digital capture, one should review compression, file formats, image processing for various uses, and system calibration (Frey and Reilly 1999).

Objective measures for defining a level of quality are useful for documenting how the source material was captured, in terms of tone, detail, noise, and color reproduction (Frey and Reilly 1999). Other standards, such as those related to using a consistent file size and format and recording the digital camera settings, can also be valuable. New formats such as Tag(ged) Image File Format (TIFF) and encapsulated postscript (EPS) will automatically embed the scanning device information into the image file. Given the range of standards that have emerged, the learning curve for selecting appropriate standards can be steep, and seeking the help of a consultant can be expensive. Nevertheless, the organization that has used standards will have greater assurance that the source material being digitized today can be migrated properly and used in the future. The standards must be documented so that the person who wants to use the digital images years from now will have measurements to return to. Organizations that are using an outside service should make sure the vendor provides this documentation with the digital image.

Quantity, or achieving a desired rate of production, is also important to a successful project. An efficient workflow can raise quantity without sacrificing quality because it minimizes disruptions in flow of digital capture, editing, and processing. This translates into better handling of objects and scanning-operator satisfaction, as well. Understanding efficient workflows will help in evaluating both in-house processes and outside services. Achieving an efficient workflow is discussed in more detail in Section 4.3.

2.5.2.2 File size
It can be quicker to capture low-resolution files. They are appropriate if the use is limited to a quick identification shot. However, if the goal is to create an image that can be archived for many uses, there are other factors to consider regarding image capture. Does capturing a midsized file (e.g., 18 MB), as opposed to a high-resolution file (e.g., 70-100 MB), save time and money? Ironically, such a difference in capture size does not significantly change the number of images one can capture per day or per week. This is because most of the time is spent setting up the shot, editing the work, processing images on storage mediums, backing up the files, and changing the camera. This is the case for in-house as well as outsourced services. Therefore, it is often advantageous to digitize at the higher MB size, assuming one's goals for size are not excessive (with available technology, anything larger than 100 MB per image may affect production goals).

Regardless of what size is to be captured, an analysis of server systems and storage-management schemes for backup and archiving is necessary to determine the potential costs of storing and migrating these files. It takes longer to open and edit a large image file than it does a small image file. It also takes more time to view multiple images simultaneously when files are large. Therefore, there are cost implications in terms of computer upgrade requirements of RAM, VRAM, additional hard drive space, and processing power. (Larger file sizes will cause similar problems in a networked environment as well.) Often, additional computers are needed to isolate the tasks of capturing and editing large files so that the computers can efficiently handle the imaging tasks pertinent to large files. Because additional computers, upgrades, or network needs can become necessary sooner than is expected (often within the first three months), it is wise to budget funds for such expenses.

2.5.2.3 Computer costs
Unplanned computer costs often relate to managing the image workflow in the studio and are based on problems that arise during the production stage. The following scenarios describe unexpected computer problems that would incur additional costs:

3.0 Analyzing Characteristics and Conditions of the Source Images

As discussed in Section 2, a complete needs analysis addresses the scope and goals of the digital project. But the best-laid plans can go awry if the characteristics and conditions of the original or source surrogate are such that they prevent digital capture. An assessment of the source images includes an estimate of the number of objects to capture, examination of their formats and characteristics, identification of the critical features that need to be retained (e.g., detail and pictorial content), and an evaluation of their condition and disposition (to decide, for example, whether to retain or dispose of the "original" source material). The results of this analysis will affect the decisions about handling the originals during digital capture, the methodology to choose (e.g., whether to capture from the original or from the film intermediate), and the appropriate digital equipment for the image quality required.6

3.1 Estimating the Number of Images to be Captured

The total number of objects to be digitized is actually less important than the number of works of a particular source format to be digitized. In a hypothetical collection of 50,000 works, 5 percent may have existing film intermediaries (i.e., slides, transparencies, or copy prints) while the rest are original materials. Of the original materials, most are 8" x 10" silver gelatin prints, and the rest are oversized (30" x 40") color photographs or daguerreotypes. These numbers suggest that scanning existing film intermediaries would complete only a small percentage of a project. The project manager needs to decide whether to create new film intermediaries for 95 percent of the originals and then scan them or to capture directly from the original materials. The latter would require equipment capable of handling the various sizes, and this, in turn, affects the selection of equipment.

3.2 Source Formats: Film Intermediaries Versus Original Sources

In analyzing the condition and characteristics of the source to be digitized, it is important to consider its format. When scanning from intermediaries, the formats could include slides, transparencies, copy prints, and microfilm. When digitizing from the original source material, it is necessary to determine whether the originals are black- and-white or color photographs, glass-plate negatives, drawings, prints, or maps.

When film intermediaries are being scanned, it is necessary to identify the quality of the intermediaries and determine whether they will be retained after the digital files have been created. In some cases, the film intermediary is retained because of its archival value, and a digital copy is created for access for use alongside the film intermediary. While it is common to retain both film and digital versions when the film is deemed to be the preservation copy (Chapman, Conway, and Kenney 1999), it is also common to retain them when the film intermediary itself is the collection (e.g., a slide collection) and is significant because it is the original material. Film intermediaries are also retained when the purpose of creating the digital file is simply for access because it lacks sufficiently high resolution for long-term archival storage.

For institutions that are digitizing original materials for long-term archival storage and access, however, the role of the film intermediary as an appropriate surrogate has come into question. Should one digitize from the film intermediary or from the original material? After being digitized, is the film intermediary retained only as a backup to the digital file? If good film intermediaries exist, they are often scanned before one decides how to digitize the rest of the material. Scanning from an existing film intermediary is useful because the original need not be physically handled, but it does require that the film intermediary be of good quality (not faded or scratched) and of first-generation (Ester 1996, as quoted in the Image Quality Working Group 1997).

In cases where no intermediary exists, one must decide whether to digitize from the original, using direct digital capture, or to use traditional photographic equipment, create the film, and scan from the film. Scanning from film is no longer considered the optimal solution for digitizing original two-dimensional works, for two reasons. First, creating photographic intermediates entails the significant added cost of making a good photographic copy. Second, with the advances in digital capture, one can now create a digital record of equal or better quality than film and thus bypass the use of film entirely for two-dimensional objects. Moreover, keeping a film copy of the digital file for comfort purposes is neither necessary nor financially justifiable, except in preservation projects where the film is produced with a specific purpose in mind. Direct digital capture requires an investment in equipment and upgrading studio space that may be initially costly. Nonetheless, after the initial investment is made, the institution can be self-sufficient and build internal capability. If initial investments are prohibitive, then one can consider outsourcing: commercial operations can provide studio setup, staff, and rental equipment if the transport of objects is feasible. Sometimes it is possible to develop a digital studio gradually. Much of the photographic equipment from the traditional studio, such as cameras, lighting, copystands, light meters, and densitometers, can be used in the digital studio.

3.3 Size of the Source Originals

The size of the originals influences the equipment used for digital capture. It may be necessary to adjust or customize the equipment to accommodate the size of the materials. Often, a copystand has to be configured to help maintain the physical relationship of the parts to the whole (as in the case of scrapbooks, albums, and sketchbooks). Working with vendors, institutions have found ways to create cradles for fragile materials or expand the size of the scanning table to accommodate oversized works. Specific considerations relative to size are discussed in the next section.

3.4 Unusual Characteristics and Features

Analyzing the unusual characteristics and critical features of the source material can help determine the best way to develop specifications for digital capture. The following examples provide general guidelines for analyzing materials that vary in size, have physical relationships to a whole, have mounts or mats, or are oversized.

3.4.1 Varied Sizes

Original items that vary in size can be difficult to digitize. The following questions are relevant:

3.4.2 Physical Relationships to the Whole

When digitizing materials that have physical relationships to the whole, care should be taken to maintain those relationships. For example, when capturing an album, the following issues must be considered:

3.4.3 Mounts and Mats

Institutions digitizing items that are mounted or attached to mats (e.g., photographs, drawings, or prints) should consider these features in the digital capture process. The following questions should be considered (Hermanson 2000):

3.4.4 Oversized Materials

Digital capture of oversized materials presents the following challenges:

Columbia's Oversized Color Image Project is a good example of how one institution analyzed the unusual characteristics and features of its source material. This digitization project had three goals: (1) to preserve the illustrative fidelity of oversized color maps, (2) to make the information accessible online, and (3) to create a large-scale printed version for access. Scanning maps presented challenges that were very different from those associated with scanning other visual materials. Capturing the smallest details at each level was important and helped determine the level of resolution the project managers aimed to achieve (Image Quality Working Group 1997). Other unique issues included how to scan maps larger than 20" x 30" and whether tiling would be appropriate. Tiling involves scanning sections and then knitting them together-a delicate task that requires a great deal of accuracy and precision (Yehling Allen 1998).

Columbia and other institutions that scan large-scale color maps continue to investigate how new digital technologies can be effective in capturing unusual characteristics of source materials. For example, the Library of Congress is using a high-resolution flatbed scanner to digitize directly from the original maps (Fleischhauer 1998). The scanner provides a strong dynamic range, a feature that is important for deciphering minute subtleties in tonal detail found in most maps.

3.5 Condition and Disposition of Originals

An analysis of source materials includes an assessment of their condition.
Materials must be examined for cracks, warping, bending, brittle bindings, or losses. Before digitizing, one must determine whether any pre-capture treatments are required. This is important to consider in advance, because after the item captured, as long as the digital archive exists, the digital file will represent the nature of the original, with its inherent cracks and scratches. It is also necessary to determine whether the original intermediate surrogates will be retained or discarded.

The condition of the source material helps determine what methodology is feasible for digital capture. Two-dimensional materials, such as original photographic prints, glass-plate negatives, drawings, prints, and oversized maps, have special handling requirements. For example, photographs are sensitive to light, maps need to lie flat, and albums must be cradled to avoid stress in the binding. The handling of source materials during capture should not exacerbate existing defects. In conjunction with conservationists, curators, and digital photographers, the institution should create guidelines for handling the objects or surrogates, determine transport procedures, and define procedures for capture of unique objects or surrogates that are sensitive or brittle. (A surrogate may be the only record of a visual object if the original no longer exists or is missing.)

The choice of equipment for digital capture depends on how the object must be handled. Flatbed scanners are more commonly used for scanning film intermediaries than for scanning originals. High-end flatbed scanners can produce both excellent resolution and great dynamic range that often exceed the standards set by the archive. Scanners typically accommodate materials of up to 9" x 11", but some scanners have larger beds. These scanners can hold several surrogates at once, leaving room for the placement of gray-scale and color bars as part of the documentation.

When one is digitizing from the original object, a flatbed scanner is not always appropriate because it requires the material to lie completely flat and not to exceed a specific size (DeNatale and Hirtle 1998). This technique may not be appropriate for sensitive materials because an unmatted original would have to be pulled up from the corners as it is placed on and removed from the glass. The flatbed scanner also makes it difficult to control light and ultraviolet levels because the light sensors are often set within the unit and cannot be changed.

Flatbed scanners, however, can be customized in creative ways. Some companies (e.g., Luna Imaging in Venice, California) have devised ways to customize commercial flatbed scanners to accommodate the overhang of the mat on the unit so that original flat works (if measuring 9" x 11" or less) do not have to be removed from their mats.

When digitizing original materials, a better option is direct digital capture, which uses digital cameras or digital camera backs attached to traditional cameras. It offers more versatility for capturing two-dimensional originals (DeNatale and Hirtle 1998). Using digital camera backs to capture the original material replicates the setups of traditional photographic studios. Because the workspace is flexible, sensitive items can be treated individually, lighting can be adjusted for different sizes and shapes, and procedures for handling and capture can be adjusted (e.g., a decision about whether to place glass over an image during capture can be made for each piece). This approach can also accommodate oversized materials, unusually shaped two-dimensional works, or unique materials such as glass-plate negatives.

From the perspective of conservation, the level of light is a critical concern when digitizing directly from originals. Direct digital capture setups require approximately four times more light than does traditional photography. Using customized setups or different lighting solutions, or both, can ameliorate the concerns about excessive levels of light. For example, halogen light produces a great amount of heat and thus is potentially problematic. Some companies have developed light housings that block most of the heat caused by halogen.8 These specialized halogen methods were used in the Vatican library project (Mintzer et al 1996). Some museums have also evaluated alternative to halogens9, such as HMI or fluorescent lights, which conservators have deemed acceptable.

4.0 Developing Appropriate Capture Specifications and Processes

Articulating the project scope and goals through a needs analysis, as well as evaluating the characteristics and conditions of the source images, are preliminary steps to digital capture. These activities also specify the appropriate capture specifications and processes. The specifications and processes for digital capture are then implemented and subjected to a technical evaluation.

4.1 Image-Capture Specifications

Image-capture specifications can be viewed as parameters of the following items:

The parameters selected depend on the goals of the project and are subject to the constraints imposed by the conditions of the source material(s) as discussed in preceding sections.

4.2 Testing and Evaluation

Once parameters have been defined, it is necessary to determine whether the equipment under consideration is capable of satisfying the specifications. In turn, one can use digital equipment to evaluate the appropriateness of the capture specifications. This can be achieved by testing the digital equipment and testing the images for their intended uses before the project goes live. This evaluative phase can also be used to assess quality-control standards and workflow.

Testing and evaluation involve considerations of the digital capture equipment, the level of detail captured, the image capture and editing capabilities, and the image capture rules.

4.2.1 Digital capture equipment
Whether digitizing from film intermediaries or the original materials, the following steps can be taken to compare digital capture equipment (i.e., flatbed scanners, digital cameras, and digital camera backs). The results should determine an appropriate component for the project (Serenson Colet, Keller, and Landsberg 1997-1998).

  1. Compare price and quality.
  2. Evaluate software for image adjustments and color-management tools.
  3. Check for artifacts (defects in the capture equipment).
  4. Look at the spectral sensitivity of the digital capture device.
  5. Evaluate speed of capture time and usable exposure time.
  6. Review lighting requirements.
  7. Identify handling concerns that the equipment imposes.
  8. If necessary, consider customized solutions for the digital studio (e.g., for lighting or a copystand that holds the original).

4.2.2 Level of detail captured
Remember that the level of detail to be captured is directly related to the size of the digital file to be archived. When capturing posters or maps with small text where legibility is critical, the equipment will have to accommodate both the size and detail required. Small originals may not require as high a resolution, but the equipment does need to capture a good dynamic range to pick up shadows or minute subtleties in the original. There may be slight differences in the ability of different devices to capture this information.

4.2.3 Image capture and editing capabilities
While testing the equipment, the user should also experiment with the image capture and image editing capabilities such as adjusting contrast and cropping. Images intended for a specific project, such as a Web site, can be optimized for the particular application at the time of their capture. For such applications, the equipment should be capable of generating an optimal capture. However, if one decides to capture the image and optimize it later, the equipment should be able to capture and store information with more neutral controls (e.g., minimal adjustments and without sharpening). The images can then be uniformly changed for the varied applications. This way, they can be used for many purposes and saved without a specific application in mind.

4.2.4 Image capture rules
In the initial stages, deciding upon the image capture and editing rules can be difficult because it requires projecting how the users will use or access the digital images. Consequently, the process is an iterative one, in which images are captured, edited, and tested for their intended use(s) and the feedback from that process is used in the next iterative step. For example, if the images are used for a Web site, it will be necessary to test whether the resolution quality chosen is appropriate for the intended audience. If the images are used for high-resolution printing, one must work with the publications department or printer to perform printing tests of the digital files. Run a press proof to determine the quality of the image and whether it will be suitable for printing to your institutional standard. Whether the project is done internally or with the help of an outside vendor, the importance of these evaluations can not be overstated. Much will be learned during the tests. In fact, one should expect to continue going through iterative processes of testing and refinement even after the project has moved beyond the evaluative phase.

One of MoMA's digital initiatives provides a good example of the importance of testing and evaluation. MoMA's digitization team includes individuals with a range of managerial and technical expertise.10 In 1997, MoMA embarked on an ambitious project to digitize 25,000 original photographs from the museum's collection. The digitization team used direct digital capture to digitize works of artists such as Edward Weston, Edward Steichen, and Man Ray. No film is used to create the digital reproduction. These digital surrogates are created with consistent standards that are appropriate to the institution's needs for archiving and access. They are used for the museum's Web site, collections- and exhibitions-management system, educational kiosks, and high-end book production. The museum has succeeded in creating digital files that can surpass the quality of film in tonal fidelity, an important criterion for printing black-and-white, duotone, and tritone photographic books. It has also succeeded in creating an archival capture that can be used for many access projects. The key to MoMA's success was the planning, testing, efficient workflow, and immediate use of the growing digital archive for a variety of applications.

4.3 Efficient Workflow

Efficient workflows are essential to the success of digital projects. Digital projects are research projects, but they also have to be productive to be financially feasible. Traditionally, museums, libraries, and archives have emphasized quality and downplayed the importance of production. But unless productivity rates are acceptable, financial investments cannot be realized. Aware of this, many institutions are realizing they can create a good workflow that will maximize the output efficiency of their studios. To do so requires that everything in the studio-the initial handling of original material, the image capture, the image editing, the movement to image storage, and the eventual image transfer for online access-work as a high-quality assembly line. Digital experts can teach us a great deal about production. Süsstrunk (1998) provides a comprehensive case study of a digital workflow production.

The following are recommendations for an efficient workflow.

  1. Staff the studio with equipment operators who respect the original material but can also work on repetitive production-oriented tasks.
  2. Set up a physical workspace that is conducive to the safety of the originals and the workers. Digital capture operators should have comfortable work setups when doing repetitive tasks.
  3. Balance quality controls with production targets for an efficient workflow.
  4. Chase the bottlenecks in the production flow: as one is removed, another may arise.
  5. Keep administrative tasks (storing metadata) to a minimum. Unless a dedicated staff member in the studio is assigned to do this in the assembly line, this task should be done outside the studio.
  6. Consider ways to continue the workflow outside of the studio (storing the master image, disseminating the derivatives, and creating an enterprise-wide solution for archiving and accessing). An institution that is not set up for the massive organization that is required once the digital file leaves the studio, may have to secure outside services for this purpose.
  7. Organize work in batches (i.e., by size and by like medium) for maximum efficiency
  8. Determine where the archive will be stored (internally or off-site)
  9. Determine where the archive will be managed (internally or off-site)
  10. Determine whether and when to refresh mediums (preparing for migration)

4.4 Documenting the Decision-Making Process

All decisions associated with planning a digital project must be documented. Keeping a record of the institutional and technical evaluations will help future staff members and others understand why certain decisions were made. Making and revising these decisions should be a group effort, because various degrees of expertise are required at various times. One should also document the procedure for handling materials (i.e., the procedure for when the work enters and leaves the digital studio during which it is captured, and the digital file prepared for access and archival purposes). Analyzing this workflow will help identify bottlenecks. The workflow will continually be revised as the team improves or changes methods in the digital studio11 .

It is also important to document what digital and computer equipment is being employed and the particular settings used. This will be helpful when one has to identify problems with the equipment or go through the process of migrating digital files. Knowing how the digital images were created will provide good information when change is required.

It is important to document the following information related to image capture, editing, and processing:

5.0 Conclusion

The products of a digital imaging project can have many different uses. This paper has stressed the advantages of using a use-neutral, rather than a use-specific, approach whenever possible. Creating a high-quality, long-term archive will ultimately help an institution benefit from the investment of time and money that these projects require. The decision-making process must be documented so that particular justifications become explicit when images are used in specific production tasks (e.g., the publication of an exhibition catalog). The following guidelines are offered for documenting the decision-making process for a use-neutral approach:

This guide has covered the process of planning a digital project, from the initial planning phases, in which the scope and goals are defined, to the analysis of source material(s) to be digitized, to the process of defining image capture specifications and image capture procedures that are then iteratively evaluated. If this process is followed closely, the result should be an efficient workflow and a successful digital project.

Footnotes

1. Refer to Stephenson and McClung (1998) and Gill, Gilliland-Swetland, and Baca (1998) for more information on preparing digital images for end uses. Return

2. Further information about printing from digital files can be obtained from MoMA's Publications Department (M. Maegraith, M. Sapir, and C. Zichello). Return

3. For a detailed analysis of migration issues, refer to Hedstrom and Montgomery 1998. Return

4. Süsstrunk (2000) notes the following: "The dpi resolution indicated by printer manufacturers usually (but not always) refers to the addressable resolution of that printer. That means that the printer can put that many dots of ink on paper per inch. However, the dots on the paper overlap, and the ink spreads depending on the surface characteristics of the paper (uncoated paper induces more spreading, and therefore has a lower resolvable resolution than coated paper). Therefore, the 'resolvable' resolution of a printer is always lower than the 'addressable' resolution." Return

5. In spring 1999, NISO, CLIR, and RLG cosponsored the Technical Metadata Elements for Images Workshop in Washington, D.C. that drew digital practitioners from various institutions. The goal of the workshop was to start setting digital metadata standards in the museum, library, and archives communities. Return

6. The questionnaire featured in Harvard's Image Scanning Guidelines is helpful in evaluating these issues (Technical Working Group, Visual Information Access Project 1998). Refer also to Conway 1999 and Ayris 1998 for further guidelines on assessing source images for scanning. Return

7. Refer to Yehling Allen (1998) for Internet sites that provide excellent guidance on how to make large images available to users electronically. Return

8. Tarsia Technical Industries in Fairfield, New Jersey, is one such company. Return

9. Photographers from the following institutions have been researching alternative lighting solutions for direct digital capture: Kate Keller and Erik Landsberg at MoMA, David Heald at the Guggenheim, Michael Bevans and Andy Proft at the Johnson Museum of Art at Cornell University, and John Wolffe at the Museum of Fine Arts, Boston. Return

10. The digitization team included digital technicians, the director and assistant to director of photographic services and permissions, the chief curator, assistant curator, chief fine art photographer, senior fine art photographer, publisher, and post processor. Return

11. For a detailed matrix for decision-making, the reader is referred to Hazen, Horrell, and Merrill-Oldham (1998). Return

Acknowledgements:

Although the chapter is written by a single author, it reflects the accomplishments and knowledge of the original digital team that forged new improvements in digital imaging at the Museum of Modern Art. These resources may be used to find out up-to-date information about MoMA's digital projects.


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