Digital Reformatting of
Photographic Formats
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Aaron Choate
Digital Library Production Services
The University of Texas Libraries
Quality Control
quality control
Prerequisites
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Identify your products and goals
quality control
Prerequisites
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Agree on your standards
Determine a reference point
Understand the limitations of current
knowledge, practice and technology
quality control
Setting up your QC program
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Identify Scope
• Whole collection or a sample of images?
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Setting up your QC program
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Determine methods
• View the image at 100%
• Use grayscale and color targets to evaluate
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color visually
Use histograms
Examine printouts
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Setting up your QC program
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Control the QC environment
• Hardware configuration
• Sufficient RAM
• Fast enough processor
• Large enough monitor
• (CRT vs LCD)
quality control
Setting up your QC program
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Control the QC environment
• Image-display software
• Choose a software package that is known to
display images accurately
• (Photoshop is a good bet… )
quality control
Setting up your QC program
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Control the QC environment
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Monitor set-up
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Calibrate your monitors regularly
Gamma should be set to 2.2
White point temperature should be set to 5,000 kelvin
(noon day sun)
Let the monitor warm up for at least 30 minutes
Reduce the room’s lighting levels if possible
Clean your screens …
Avoid turning the monitors on and off often if
possible
quality control
Setting up your QC program
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Control the QC environment
• Color quality control instruments and software
• Monitor calibrators
• Densitometers
• Colorimeters
•…
quality control
Setting up your QC program

Control the QC environment
• Color management
quality control
Setting up your QC program
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Control the QC environment
• Viewing conditions
• Keep windows shaded
• Reduce overhead lighting
• Reduce glare on the monitors (face walls, not
windows…)
• Try to shield the viewing space for the original from
the monitor
• Inspect images against a neutral gray background
(turn off your desktop patterns)
quality control
Setting up your QC program
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Control the QC environment
• Human characteristics
• Because each person sees color differently, it
would be ideal to have one person do all the QC
for a batch of images.
• Otherwise, come up with an effective way to
communicate about color
quality control
Setting up your QC program
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Evaluate system performance
• System tests prior to conversion –
• Resolution
• Linearity (dynamic range)
• Flare
• Scanner noise
• Artifacts
• Color reproduction
quality control
Setting up your QC program
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Codify your inspection procedures
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Assessing Image Quality
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Evaluate:
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Resolution
Questions to ask
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Is the stroke adequately reproduced?
Is the significant detail adequately reproduced?
Is fine detail in the darkest and lightest portions
retained?
Are there even gradations across the image?
Is the image free of moire effect?
Is the significant informational content adequately
reproduced?
Is the document fully reproduced?
Is the image too light or too dark?
quality control
Assessing Image Quality
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Evaluate:
• Color and tone
• Histograms
• Avoid clipping
• Color and Grayscale targets
• Measuring RGB values
Tips
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Decide on whether you want to include the
target in every image or if you want to image
the target once during a scanning session
Choose a place in the scan range that will
maximize your ability to capture data
Replace your targets on a regular basis
Sample scans of targets should be captured
with your project metadata
Questions … grayscale
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Are the details in the sections of the document
captured?
Is the image too light or too dark overall?
Use your grayscale bar to test:
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How many bars can you identify?
Where do you cease to discern distinct shades
Do you see a color shift?
How do the RGB values compare to the reference
values?
Are all digital levels (0 – 255) used? Is there any
clipping?
Questions … color
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Do you observe a color shift?
Is the image light or dark overall?
Compare the grayscale values as
before.
Compare the color values to the color
target.
Is the color satisfactory?
quality control
Assessing Image Quality
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Evaluate:
• Overall evaluation
• Does the image convey all of the significant
information
• How would you rate the image as compared to the
original? (unacceptable, adequate but diminished,
comparable, improved)
• Will the potential user be satisfied with the image
as a surrogate?
• Is the image’s dynamic range adequate?
• Are you satisfied with the color appearance?
Examples:
AAA – Spanish Colonial Arch.
http://www.lib.utexas.edu/photodraw/missions/
BLAC – Sanchez
http://www.lib.utexas.edu/photodraw/sanchez/
CAH – Photojournalism & Am Pr
http://www.cah.utexas.edu/photojournalism/index.php
CAH – Robert Runyon
http://runyon.lib.utexas.edu/