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CHOOSING BOOK
AND BOUND DOCUMENT SCANNERS AND ACCESSORIES
A quick comment
on the use of the term "IMAGE QUALITY"
Of course image
quality is affected by such factors as MTF, number of
active photo sites on a sensor, signal to noise ratio, pitch
and diameter of the photo site, bit depth, sampling schemes,
processing algorithms, quality of A to D conversion, Dmax,
and the quality of the lens. Most often, people
believe mistakenly, that the "resolution" measured
in PPI (pixels per inch; DPI is a printer measure) equals image
quality. That is not the case-- resolution is a complex interaction
of all the above factors. Equally, at the most demanding
end of imaging, users judge the image quality of a scan by the
qualities of the raw (right off the scanner) image before any
imaging software processing enhancements are added. High end
archiving is a purist's world. However, image processing is more than acceptable
for archiving other than pure data. Therefore, the phrase "image
quality" is the end result of capture and post processing.
Comparing "image quality" without consideration
as to the intended end use of the image results in confusion and is not comparing apples
to apples. The archive "raw file" after post-processing is a derivative called a "service" file.
When we consider
"Book Scanners" we should really use a pragmatic definition
of image quality which is related to the purpose and use of
the end product and the imaging requirements of the user.
The following table seeks to offer that perspective, since good
image quality is relative to accomplishing the intended purpose
of the scanner.
| PURPOSE |
PRODUCTIVITY
LEVEL
|
EXAMPLE |
| High Level
Archiving for Preservation, Conservation, Print Reproduction,
Derivatives for Electronic Dissemination.
Most Fragile and Rarest
Books & Special Collections
|
Low/Moderate |
AIAxact Integrated Book
Scanners |
| Archiving for
Preservation, Conservation, Print Reproduction, Derivatives
for Electronic Dissemination.
Special Collections and
General Circulation
|
Moderate |
I2S DigiBook |
| High Quality
Access to Special And General Collections with Automated Page Turning |
Highest |
I2S D-Line
|
| Inter Library
Loan Electronic Dissemination |
High |
|
| Personal Scans
For Content Only |
High |
Image Access KIC
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Selecting a
book scanner is a process of eliminating off-setting tradeoffs:
- speed for image quality;
- convenience for size and flexibility;
- all the aforementioned for cost.
To better conceptualize the choices, we have arbitrarily divided
all book scanners into two categories:
- Book scanning machines--all components are from one manufacturer,
designed for maximum throughput and productivity, providing
software for image processing and correction of book curvatures,
and supplying everything in a neat ergonomic package;
- Integrated digital photographic systems that put together
photographic components of different manufacturers such as
cameras, lights, lenses, copy stands and book cradles to meet
specific needs and maximize image quality (much like a component
stereo system).
Book scanning machines are designed for a single purpose...to
scan books. They have tables with built-in cradles, special tracking
lights or fixed lighting, fixed focus lenses, and allow operators
little or no latitude to manipulate basics such as exposure, scan
time, and focus. Most adjustments to the "look" (contrast,
brightness, sharpness) of the scan is either made in batched post
processing software, or done on the fly as presets. Additionally,
the book scanning machines often come with Book Imaging Manipulation
Software to correct the curvatures of pages, sharpen the edges
of type, convert RGB to b/w and grey scale, etc. Their forte is
easy operation and the fastest possible throughput.
Integrated component book scanners take various components (lenses,
cameras, lights, copy stands) from photography, add a digital
scan back, specialized lights (no heat and low UV), a book cradle,
and mimic a photographic workflow. The initial design intent is
image quality, color accuracy, flexibility and control. The main
benefits are flexibility in choosing the components (e.g., most
if not all book scanning machines offer 180 degree cradles), the
ability to capture oversized material, and pure image quality
which in most cases surpass the performance of most of the book
scanning machines.
However, the workflow is photographic. The systems are slower
than the book scanning machines, and most do not offer book-specific post-processing image manipulation. Any "fixes" (like
curvature) must be photographically corrected before the scanning
(e.g., using a piece of glass to hold a page flat so there is
no curve, or increasing the depth of field to hold focus for a
large amount of pages). But arguably, when speed is not the only
criteria, these systems produce better images at ultra high resolutions,
produce more accurate color reproduction, and lend themselves
to the slow process of handling rare, fragile and oversized books.
Before researching specific products, you may want to consider
your answers to the following questions:
- How large is the collection (in estimated pages)?
- Will this be an ongoing effort beyond a specific collection?
- What experience, expertise, etc., will be required of existing
staff or potential operators?
- Will the scans be archival?
- Will the scans be for the Web only?
- Will scans be for print reproduction?
- How much space is available for housing the scanning operation?
- What is the maximum physical size of books to be scanned?
- Is curvature correction required?
- Is image quality paramount?
- Does color capture have to be as accurate as possible, or
"'representational" of the original?
- Is it important to capture the aesthetic as well as the
legibility of the content?
AIA would be happy to discuss your answers to these and other questions or issues you may have. We have a
comprehensive line of book scanning technology and accessories
represented by the links on this page. We would be happy to provide
more information, answer your questions, help you figure out what
best fits your application, and even customize or design equipment
to meet your needs.
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Academic
Imaging Associates
P.O.
Box 192, 172 Carlen Street
Manchester Center, VT 05255
V 802.362.3169 F 802.362.0760
Academic Imaging Associates
Manufacturers of Technology, Lighting and Devices
of Interest to Digital Libraries,
Archives, and Scientific Institutions
BetterLight, Jenoptik, Metis, TTI Tarsia
Technical Industries, AIAXact, Creo, Sinar, Kaiser,
Linhof, Rollei, Schneider, Rodenstock, Imacon, PhaseOne,
Nikon, Fuji, Microptics, Zig-Align, Kodak, Leaf, Cruse,
Bogan, Bessler, Bassant, Zeiss, Sony, JVC, Braun, Kigamo, I2S D-Line, I2S Digibook, , Buhl, North Light, Dessanti, nNovia, Novoflex, Bogan, Panoscan, Canon, Comprehensive, ProVideo, Panasonic, Cambo, Epson, Contax, Colortrack, Eldim, Pixera, Riser, Hasselblad, Mamiya, Image Access
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