Guides

Guides to Quality in Visual Resource
Imaging
July 2000
© 2000 Council on Library and Information Resources
Contents
Background
Introduction
1. Planning an Imaging Project, by Linda Serenson Colet, Museum of Modern Art
2. Selecting a Scanner, by Don Williams, Eastman Kodak Company
3. Imaging Systems: the Range of Factors Affecting Image Quality, by Donald D'Amato,
Mitretek Systems
4. Measuring Quality of Digital Masters, by Franziska Frey, Image Permanence Institute
Rochester Institute of Technology
5. File Formats for Digital Masters, by Franziska Frey
References & Further Reading
About the Authors
Background
In 1998, the Digital Library Federation, the Council on Library and Information Resources,
and the Research Libraries Group created an editorial board of experts to review the state of
the art in digital imaging of visual resources (original photographs, prints, drawings, maps,
etc.). While sources for instruction in digitizing text or text and images existed and were
growing, none specifically addressed the challenges of two- and three-dimensional, as well
as color-intensive, materials.
Charged to identify imaging technologies and practices for such visual resources that could
be documented and recommended, the board arrived at a set of guides in the science of
imaging—objective measures for image qualities and how they can be controlled in various
aspects of the imaging process. With detailed outlines created by board members, DLF and
CLIR commissioned board-recommended authors, and have published the guides on the
Web with RLG.
Guides to Quality in Visual Resource Imaging Home
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These five guides are designed to serve the growing community of museums, archives, and
research libraries turning to imaging as a way to provide greater access to their visual
resources while simultaneously preserving the original materials. They will be updated
periodically. Your comments are encouraged by DLF and RLG.
Introduction
Museums, archives, and libraries worldwide are converting visual resources into digital
data, and in each case managers of those conversion programs face the same series of
decisions about how to create the best possible image quality. These guides bring together
the expertise and experience of leaders in the field of visual and color imaging and make
their knowledge widely accessible.
The guides are written for those who have already decided what they will digitize and what
purposes the digital images will serve. After the often-complex matters of selection have
been settled, these guides address the steps to successfully create and store high-quality
digital masters and derivatives. They include project planning, scanner selection, imaging
system set-up, and the resulting digital masters.
Guide 1, planning, underscores the importance of defining the users' needs and requirements
before undertaking the project. Best practices in digital visual resources include creating
images that meet quality and use objectives and documenting how the image being delivered
was created. Guide 2, finding the right scanner, starts from a knowledge of the source
material to be scanned and, by looking at how to interpret product specifications and employ
verification tests, equips users to evaluate new machines as well as those now on the market.
Similarly, for setting up the larger system of scanner, camera, operating system, and
image-processing software, guide 3 provides information, techniques, and procedures that
can be used now and into the future. Guide 4 deals with digital masters, focusing on
developing "visual literacy" in digital imagery and quality assurance; and guide 5 addresses
the effect that different file formats—the containers—have on the performance and
persistence of digital masters over time and technological change.
While there are few universally applicable answers to the questions faced by those who plan
and carry out visual imaging projects, the writers of these guides identify critical
decision-making points and offer concrete guidance based on the purposes of the images.
Where possible, they provide objective measurements of image quality. At the same time,
they flag areas where further research and testing are needed before specific practices can be
recommended. Each guide is a module that can stand on its own to be mined for
information. As a set, the guides provide guidance on how to find what you need to
accomplish your stated goals with the available technology, whatever its state of evolution.
And they help to clarify the consequences of trade-offs that all managers must make to stay
within their means.
In providing this framework, from planning to digital output and perpetuity, this publication
is intended to offer value both to practitioners and to those who must judge whether a digital
imaging effort is feasible, well planned, and worth supporting.

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Guides to Quality in Visual Resource Imaging
1. Planning an Imaging Project
Linda Serenson Colet
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
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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:
ppi (pixels per inch) refers to on-screen or digital resolution and should be used by
those who are creating the image files. The most common screen resolution is 72 ppi.
However, some high-end monitors can display more, 84-200 ppi (Austen 2000).
Digital resolutions vary according to the specific device. Scanners for hard copy
(reflective) material range from 300 ppi to about 1,200 ppi. Scanners for transparent
material (film) range from 300 ppi to about 8,000 ppi.
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dpi (dots per inch) should be used when talking about printers that refer to "d" as a
printing dot (e.g., ink jet printers, laser printers). For example, many color ink jet
printers have a resolvable resolution of 300 dpi.4 To optimally reproduce an image,
the resolution of the scan should be 300 ppi. Note that some scanners still use the
term dpi to indicate scan resolution.
q
lpi (lines per inch) should be used when talking about printing (offset, gravure) in
which "l" describes the lines of the halftone screen. For example, many museum
publications are printed with halftone screens of up to 200 lpi. To optimally reproduce
an image at 200 lpi, the digital file should have a ppi resolution of 1.5 to 2 times the
screen frequency (i.e., 300-400 ppi).
q
The number of channels is determined as follows:
Single channel: for gray-scale or monochromatic pictures as well as for the reduced
color palette used by the Web.
q

Three channels: a full-color picture on the monitor requires three channels: red,
green, and blue (RGB). It requires three times the amount of data as a single-channel
picture. Archival files are usually stored in RGB.
q
Four channels: An offset reproduction requires four channels: cyan, magenta,
yellow, and black (CMYK). A copy of the archival file is converted to CMYK by
printers for reproduction.
q
(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
reallocate existing staff or hire new staff to manage the project, consider the
technology choices, and operate the equipment;
q
design a studio space that includes customized adjustments to accommodate the
digital project (e.g., air conditioners and ultraviolet shields to protect against heat, air
filters to minimize dust accumulation, and places to store and view originals that are
being digitized);
q
perform an extensive on-site technical evaluation of digital equipment;q
purchase or rent equipment necessary to run the digital studio (e.g., digital scanners or
cameras, lighting, copystands, and processing equipment such as CD, DVD, or tape
drives);
q
train current and new staff on the use of equipment;q
hire or use technical staff to organize the system integration, resolve networking
issues, design a storage system, and manage the transfer of image files from the studio
to users' desktop machines;
q
administer logs that record digital metadata, which are essential to ensuring that
information can be migrated effectively;5
q
pay consultants to advise on production processes that balance quality and the rate of
production; and
q
send project staff to conferences and classes to improve their technical and project
skills.
q
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:
Scenario 1: Digitize original materials using in-house staff but have an outside service
process the digital images onto CDs, tape backups, etc., for archival and access
purposes. This approach reduces the administrative tasks associated with digitizing,
which can often decrease the rate of image capture. This approach is recommended if
production is a priority and if there are reservations about allowing personnel outside
the institution to handle the source materials.
q
Scenario 2: Use outside contractors on-site, working with in-house staff to digitize the
materials. This approach is recommended for an organization that wants its staff to
gain technical experience in quality control while also rapidly getting the project
under way.
q
Scenario 3: Outsource the entire digitizing project, but manage the post-capture
activities in-house. This approach is recommended if the materials to be digitized are
not precious originals, but film intermediaries. It also lets the organization devote its
time to developing ways to use the digital images in its access and production projects
rather than to creating those digital images.
q
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:
paying staff or vendors to capture and archive the images;q
upgrading digital and computer equipment annually or biannually;q
paying unanticipated expenses as the project matures, such as expanded outside
vendor services, consultants, and additional staff or equipment; and
q
weekly technical maintenance on imaging computer equipment, system integration,
networking, and archival storage system management.
q

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:
Scenario 1: The scanning and editing computers are incompatible and cannot pass
images properly from one system to another. Additional costs are incurred for
technical help and possible restructuring, such as adding or subtracting computers in
the workflow.
q

Scenario 2: The amount of data being produced is causing the computers to fragment
on a weekly basis. Costs such as those in scenario 1 may be incurred.
q
Scenario 3: One or more computers crash for an undetected reason, stopping scanning
for several hours. The technician recommends buying a new computer and isolating it
from the production loop.
q
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:
Will it be difficult to find similar items to group together for capture?
If the objects to be digitized are not similar in size or type, production will be slowed.
Rearranging the setup for capture (i.e., moving the camera, changing the lighting, or
adding filters) takes time.
q
What type of setup is required to accommodate objects of different sizes?
Is a larger or wider digital capture table needed? Is there enough storage and staging
space to arrange the objects according to size, material, or status (e.g., those captured
or edited)?
q
What file sizes should be considered to accommodate original objects in a range of
sizes and shapes? If one opts to capture objects within a particular range of sizes
without moving the camera, the file size will have to vary. Additionally, many objects
are not proportionately equivalent to the square format of many camera backs. To
include all information of that object, one should consider the usable pixel areas of
the scanback to determine if it meets one's requirements for file size. (Landsberg
2000).
q
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:
What is the relationship of the parts to the whole? Can each page be captured
separately, or does one have to accommodate a binder and therefore capture two
pages at once?
q
Does the album need to be cradled to minimize stress on the binding?q
Do the album pages have intrinsic significance, or is it sufficient to capture the
images from each page? Is there a relationship between the spreads that should be
maintained, or is an indication of sequence enough to recreate the experience of
looking through the album?
q
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):
Can the object be safely and easily removed from its mount or mat for capture? If not,
can the object be captured while attached to the mount or mat?
q
If the object needs to be removed, at what level do conservators, framing personnel,
or preparators need to be involved? Who can remove an object from simple paper
corners? What about slitting hinges or removing other mounting techniques?
q
Is an original mount to be treated as part of the object, and, if so, should it be included
in the scan in its entirety?
q
If the artist has indicated that a work should be cropped, should the scan reflect this?q
If the original material must remain in its mat, what type of physical adjustments does
this require? For example, a copystand or scanning table that can accommodate an
open mat may be needed. What kind of scanning complications might arise from
reflections off this open mat?
q
3.4.4 Oversized Materials
Digital capture of oversized materials presents the following challenges:
What type of digital capture device can accommodate an oversized work? Many
customized setup solutions are available.
q
What kind of lighting arrangements are necessary to illuminate a large object evenly?q
What type of scanning judgments will be necessary to accommodate the critical
features? For example, density and type size can vary greatly with oversized materials
such as maps.
q
What compression issues need to be considered for both archival storage and
dissemination to the user? For example, an oversized map of 22" x 27" captured at
300 dpi in 24 bit becomes a 160-MB file (Yehling Allen 1998).
q
How will users' access to such oversized, storage-intensive data be facilitated? Some
sites provide tiling, several resolutions, and different details of each image.7
q
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 maximum file size for the archive,q
the required file sizes for the derivative images to be used for the access projects,q
the image editing rules, such as contrast adjustments, cropping, and dust spotting, thatq

will apply to both the archival and derivative copies (this includes whether to
optimize the images during the capture process or whether this optimization is done
outside the digital studio),
the storage format (e.g., TIFF, PCD, jpeg, flashpix) and medium (e.g., CD, DVD,
tape) for storing the digital images for archival purposes, and
q
the storage format and medium (or network setup) for storing the image derivatives
for access.
q
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).
Compare price and quality.1.
Evaluate software for image adjustments and color-management tools.2.
Check for artifacts (defects in the capture equipment).3.
Look at the spectral sensitivity of the digital capture device.4.
Evaluate speed of capture time and usable exposure time.5.
Review lighting requirements.6.
Identify handling concerns that the equipment imposes.7.
If necessary, consider customized solutions for the digital studio (e.g., for lighting or
a copystand that holds the original).
8.
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.
Staff the studio with equipment operators who respect the original material but can
also work on repetitive production-oriented tasks.
1.
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.
2.
Balance quality controls with production targets for an efficient workflow.3.
Chase the bottlenecks in the production flow: as one is removed, another may arise.4.
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.
5.
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.
6.
Organize work in batches (i.e., by size and by like medium) for maximum efficiency7.
Determine where the archive will be stored (internally or off-site)8.
Determine where the archive will be managed (internally or off-site)9.
Determine whether and when to refresh mediums (preparing for migration)10.
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:
date of captureq
type of digital capture and its characteristicsq
targets usedq
density values on gray-scale and color barsq
color-management profilesq
general profiles that connect the digital equipment in the studioq
contrast or color settings used in the imaging softwareq
type of lighting used in the capture processq
computer equipment usedq
file size, format used (e.g., CD, DLT)q
contrast adjustment recorded (e.g., black-and-white point values during image
editing)
q
file size, medium used for storage and transfer (e.g., TIFF, JPEG)q
notes relating to opening the file, if anyq
notes relating to optimizing the file for varied uses (e.g., recording the contrast or
color settings used is an important identifier for those who receive the image)
q
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:
Articulate the project scope and assess the characteristics of the source materials.q
Capture at the highest resolution possible within the constraints of the project's
resources.
q
Store use-neutral image files (i.e., keep device dependent color correction and other
optimizations to a minimum).
q
When using the stored digital images for specific production tasks, incorporate the
post-process optimizations that are specific to the task at hand (e.g., the production of
an exhibition catalog).
q

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.
Mikki Carpenter, Director of Photo Services and Permissionsq
Peter Galassi, Chief Curator of Photographyq
Sarah Hermanson, Assistant Curator of Photographyq
Kate Keller, Head of Fine Arts Imagingq
Eric Landsberg, Manager of Imaging Technologiesq
Michael Maegraith, Publisherq
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Guides to Quality in Visual Resource Imaging
2. Selecting a Scanner
Don Williams
1.0 Introduction
2.0 Source Material Characterization
3.0 Background and Definitions of Image Quality Features for Scanner Selection
3.1 Tone Reproduction
3.2 Resolution
3.3 Color Reproduction
3.4 Noise
3.5 Artifacts
4.0 Understanding Product Specifications
4.1 Resolution: DPI or Image/File Size?
4.2 Bit Depth: Gray Levels, Shades of Gray, Millions of Colors
4.3 Dynamic Range: Maximum Density, # f-stops
4.4 Examples: Interpreting Product Literature
5.0 Resources and Methods for Image Quality Verification
5.1 Tone Reproduction or Tonal Fidelity
5.2 Color Reproduction or Color Fidelity
5.3 Resolution or Modulation Transfer Function (MTF)
5.4 Noise
5.5 Artifacts
5.6 Relative Importance of Image Quality Features for Different Document Types
6.0 Scanner Review
1.0 Introduction
What is a scanner? It is more than a beige desktop box or copy stand camera. It includes the related
driver software and application programs that manage it. Some may consider this a technicality, but
if the history of desktop printers is a harbinger for capture devices such as digital scanners and
Guide 2: Selecting a Scanner

cameras, then one must treat the triad of hardware, driver software, and application as the scanner.
When choosing a scanner, all of them need to be evaluated and treated as a unit. Table 1 presents
common attributes associated with each scanner component. Some of these functions may migrate
between categories or from device to device. Most of them affect image quality in some way.
Table 1. Attributes of scanning components
Hardware Driver Software Application
Light source Number of bits per pixel Color management
Platen size Image processing Compression
Scan speed Productivity Scripting
Optics and optical path Calibration File formats
Mechanics Gamma selection
Sensor Scaling
Power requirements OCR
Factory support Raster-to-vector conversion
Electronics path Page format retention
Auto-document feed (ADF)
Transparency adapter
A scanner must be selected in the context not only of the characteristics of the object to be scanned
but also of the intended use of the scanned image. There is no sense in purchasing an expensive
scanner when the resulting images will be used only for Web site postings. On the other hand,
creating digital master files for unknown future uses requires strict attention to detail and an
understanding of how image information manifests itself and can be properly captured.
Section 2 of this guide reviews the salient categories of the source materials; namely content,
format, and optical characteristics. Section 3 contains definitions of image quality features. These
definitions are used as a basis for a discussion of setting minimal scanning requirements to achieve
suitable image quality according to source and intent. Resources and methods to measure or judge
these image quality features are described at length. Because not everyone is willing to perform
image quality measurements on their own, Section 4 presents information on the interpretation of
manufacturers' scanner specifications. Examples of such specifications, along with explanations, are
included. The guide concludes with a review of scanner types in terms of image quality and
implementation features.
2.0 Source Material Characterization
Knowing your collection and understanding the priorities for digitizing it will help you determine
the type of scanner to choose. There are four classes of scanners from which to select: film scanners,
cameras, flatbed or sheet-fed scanners, and drum scanners. Except for film scanners, there can be
considerable overlap in the content, format, and optical characteristics that each type of device can
scan. Table 2 presents source material categories according to these three features.
Table 2. Characteristics of scannable source materials
Content Format Optical Characteristics

Color Type:
•black and
white
•full color,
•monochrome
Photographs
Text
Halftones
Manuscripts
Line art
Art work
Mixed
Size
Three-dimensional (3-D)
Film (roll or sheet)
Bound/unbound
Flexible (film)/inflexible (glass-plates)
Reflection/transmission
Surface characteristics
(gloss, texture, flat/
wrinkled)
Density range
Spatial detail content
Color dye/pigment gamut
Artifacts/condition (e.g.,
scratched, fragile, torn, bent,
faded)
Some types of scanners are better at capturing certain of these features than others. Benchmarking a
scanner with respect to image quality features will delineate these differences. Definitions of these
features and techniques for evaluating their quality are covered in the remainder of this guide.
3.0 Background and Definitions of Image Quality Features for
Scanner Selection
In its purest form, image quality can be judged by the signal and noise characteristics of the image
or scanning device under consideration. The ratio of signal to noise is often used as a single measure
for image quality; that is, the greater the signal-to-noise (S/N) ratio the better the image quality.
However, because one person's signal is another person's noise, the use of SNR as an image quality
metric is difficult to manage. The interpretation of signal and noise becomes too broad and, in turn,
ambiguous. S/N can be a useful measure for characterizing scanner performance; however,
translating this measure into absolute image quality is difficult.
Consequently, image quality features are dealt with by more tractable imaging performance
categories. There are five such categories: tone reproduction, color reproduction, resolution, noise,
and artifacts. All yield objective measures that contribute to overall image quality in complex ways.
For instance, a viewer does not perceive tone reproduction or resolution but rather the
psychophysics of lightness, contrast, and sharpness. He or she then creates a mental preference for
the image. Although these categories cannot measure image quality directly, they do serve as a good
high-level model for evaluating image quality. The remainder of this section is devoted to detailed
definitions of these image quality features. It will serve as a basis for further discussions on
specifications and tools for scanner selection.
3.1 Tone Reproduction
Tone reproduction is the rendering of original document densities into luminances on softcopy
displays or into densities in hardcopy media. It is the foundation for the evaluation of all other
image quality metrics. It determines whether a reproduced image is too dark, too light, and of low
contrast or of high, and implicitly assumes the evaluation of neutral gray tones over large areas of an
image.
The seductive beauty of a photograph by Ansel Adams or Irving Penn is primarily due not to the
image content, composition, sharpness, or low noise but rather to the remarkable reproduction of
tones-from gleaming highlights to deep-shadow details, with all tones in between. Tone

reproduction is the welcome mat to the evaluation of all other image quality metrics. Although on
the surface, tone reproduction seems a simple job of tone management, the subtleties of the viewing
environment and cultural and professional preferences often make it an art.
For scanned image files, tone reproduction is somewhat of a misnomer unless a final viewing device
is assumed. This is because the capture process in a scanner is simply that-a capture step. It is not a
display that reproduces light. Tone reproduction, by contrast, requires both capture and display.
How then does one select a scanner to accommodate the best possible tone reproduction when the
scanned data generally may be reproduced on any number of display types and for a number of
viewing preferences?
Three objective image-quality attributes of a scanner—the opto-electronic conversion function
(OECF), dynamic range, and flare—ultimately and universally affect all tone reproduction. The
scanner's driver software often controls the OECF; dynamic range and flare are inherent in the
hardware.
The OECF is a term used to describe the relationship between the optical density of a document and
the average digital count level associated with that density, as detected by the scanner. The OECF is
the first genealogical link between an original object and its digital offspring and is usually
controlled by the software driver. The extent to which the driver software allows the user to control
the OECF and documentation on how the driver software accomplishes this are important features
to consider when selecting a scanner.
Dynamic range is the capacity of a scanner to distinguish extreme variations in density. As a rule,
the dynamic range of a scanner should meet or exceed the density extremes of the object being
scanned. Because specifications for dynamic range are frequently overstated, the means to
objectively verify these claims should be at hand. This will be covered in Section 4.3.
Flare is non-image-forming light with little to no spatial detail content. It manifests itself by
reducing the dynamic range of a device and is generally attributed to stray light in an optical system.
Documents in which low densities predominate and devices requiring large illuminated areas, such
as full-frame digital cameras, generally suffer from high flare. These two conditions should be kept
in mind when selecting a scanner. Whenever large amounts of light, even if outside the scanner's
field of view, are involved in imaging, flare may become a problem.
See also, Tone Reproduction, Guide 4.
3.2 Resolution
Resolution is the ability to capture spatial detail. It is considered a small-area signal characteristic.
Before the advent of electronic capture technologies, resolution was measured by imaging
increasingly finer spaced target features (that is, bars, block letters, circles) and by visually
inspecting the captured image for the finest set of features that was detectable. The spatial frequency
of this set of features was considered the resolution of that capture process. Measured in this way,
resolution values depended on the target's feature set, image contrast, and inspector's experience.
The units used for reporting resolution were typically line pairs per millimeter.
The resemblance of these units to the spatial sampling rate units of a digital capture device is
unfortunate and continues to be a source of confusion about just what resolution is for a digital
capture device. For digital capture devices, resolution is not the spatial sampling rate, which is
characterized by the number of dots per inch (dpi).

The type of measurement described above is considered a threshold metric, because it characterizes
the limiting spatial detail that is just resolvable. It reveals nothing about how the lower spatial
frequencies are handled in the capture process; in other words, the extent to which they are
resolvable. It is largely a pass/fail criterion. Because of this shortcoming, as well as feature, contrast,
and inspector dependencies, resolution measurement done in this way is not robust. A
supra-threshold metric is needed that removes not only the feature set and contrast dependencies but
also the inspector's subjectivity.
The modulation transfer function (MTF) is a metric that allows one to measure resolution in a way
that satisfies these criteria. The MTF is a mathematical transformation of the line-spread function
(LSF). The LSF is a fundamental physical characterization of how light spreads in the imaging
process, and for spatial resolution measurements, it is the Holy Grail. A detailed explanation of
MTF, its value, and how it is used can be found in Image Science by J.C. Dainty and R. Shaw
(1974).
3.3 Color Reproduction
Color reproduction, like tone reproduction, is a misnomer for scanners because colors are only being
captured, not reproduced. A more accurate term has been coined for the potential color performance
or fidelity of a digital capture: the metamerism index. International Standards Organization (ISO)
work is under way to propose a metamerism index that would quantify the color-capture
performance of a device relative to that of a human observer. The goal would be for the scanner to
"see" colors in the same way as humans do. A metamerism index of zero would indicate
equivalence between the scanner's color performance and that of a human observer. Calculation of
the metamerism index requires knowledge of the device's color channel sensitivities as well as the
illumination type being used, two pieces of information not normally provided by scanner
manufacturers. In the absence of such a measure, a suitable surrogate for color capture fidelity,
called average Delta E*, or E*, is often used.
E* makes use of a standardized perceptual color space called CIELAB. This color space,
characterized by three variables—L*, a*, and b*—is one in which equal distances in the space
represent approximately equal perceptual color differences. L*, a*, and b* can be measured for any
color and specified illuminant. By knowing these values for color patches of a target and comparing
them with their digitized values, a color fidelity index, E*, can be measured.
Finally, gray-scale uniformity may be considered a form of color fidelity. Gray-scale uniformity is a
measure of how well neutral tones are detected equivalently by each color channel of a scanner.
Although it can also be measured with the CIELAB metric, there are often occasions where the
L*a*b* values are not available. In such cases, a first step in measuring color fidelity is to examine
how well the average count value of different density neutral patches matches across color channels.
See also, Color Accuracy, Guide 3 and Color Reproduction, Guide 4.
3.4 Noise
For photographic film, noise is often referred to as "grain" or "granularity," since its appearance is
granular or random in nature. Like film, digital scanners and cameras have sources of noise related
to signal detection and amplification. The nature of this noise is similar to that of film and can be
defined as unwanted pixel-to-pixel count fluctuations of a random or near-random nature.

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