Digital Reformatting of Photographic Formats

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Aaron ChoateDigital Library Production Services

The University of Texas Libraries

Quality Control

quality controlPrerequisites

Identify your products and goals

quality controlPrerequisites

Agree on your standards Determine a reference point Understand the limitations of current

knowledge, practice and technology

quality controlSetting up your QC program

Identify Scope• Whole collection or a sample of images?

quality controlSetting up your QC program

Determine methods• View the image at 100%

• Use grayscale and color targets to evaluate color visually

• Use histograms

• Examine printouts

quality control Setting up your QC program

Control the QC environment• Hardware configuration

• Sufficient RAM

• Fast enough processor

• Large enough monitor

• (CRT vs LCD)

quality control Setting up your QC program

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

Control the QC environment• Monitor set-up

• 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

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

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

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

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

Codify your inspection procedures

quality controlAssessing Image Quality

Evaluate:• Resolution

Questions to ask 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 controlAssessing Image Quality

Evaluate:• Color and tone

• Histograms

• Avoid clipping

• Color and Grayscale targets

• Measuring RGB values

Tips

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 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:

• 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

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 controlAssessing Image Quality

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/