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Targeting for Important Color Content: Near Neutrals and Pastels
Statement of the Problem- the wrong tool for an important job -
IS&T's Archiving Conference, 2012
Today’s color evaluation and profiling targets were designed for consumer and professional photographic use cases
/Colors are meant to mimic blue sky, foliage, flesh tones,and fruit colors considered important for those imaging sectors.
/ They lack any believable color references to parchments, vellums, aged paper, or the sepia tones of early photographic processes
� Not designed to discriminate the subtle tonal gradations, and low chroma, high luminance color content that predominates cultural heritage collections.
�Metameric failure detection
� The Build
The Solution
IS&T's Archiving Conference, 2012
Design, build, and test a color imaging reference target more suited to the needs and color demographics
of cultural heritage imaging collections.
Execution
IS&T's Archiving Conference, 2012
� Conduct a color census of common and problematic colors
� Analyze color census data
� Design and build a candidate test target and analysis software
� Field test and refine the target design
Past WorkSpectral, not just Colorimetric -
IS&T's Archiving Conference, 2012
19th century photographic collection content from IPI
New Work - Color Census- beyond -
IS&T's Archiving Conference, 2012
New Work - Color Census- beyond photographic content-
IS&T's Archiving Conference, 2012
The MorganSelected vellums, parchments, and papers. (16th-19th century)
New York Public LibrarySelected papers and rare books
ISA collection18-19th century chromolithographs and watercolors
Regional historical societiesMaps
Robert Louis Stevenson marginalia,
The Strange Case of Dr. Jekyll and Mr. Hyde,The Morgan – New York City
Target Design Consideration- Reduction to Practice-
IS&T's Archiving Conference, 2012
- Intuitive spatial layout of color patches (flexible but simple)- Greater population of statistically selected census colors - Lesser population of wide gamut contingency colors- Metameric pairs- Administrative elements:
- workflow automation - data tracking and communication
- Form factor- Manufacturable- Cost
Candidate target ( v 0.1)- a better tool for cultural heritage imaging -
- A4 format- 285 unique colors- Radial a*b* color symmetry- Commercially available colorants
( some exceptions)
- 18 neutrals- 52 wanna’ be neutrals- 84 near neutrals- 131 high chroma colors
- Heavily populated vellum, parchment, paper colors
IS&T's Archiving Conference, 2012
Data Analysis- CIELAB coordinates from color census vs. candidate target -
IS&T's Archiving Conference, 2012
-60 -40 -20 0 20 40 60
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L*
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b*
L*
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b*
Candidate color target
Census data
a* vs. b* L* vs. a* L* vs. b*
A sensible approach to color capture evaluation- it’s all about choice -
IS&T's Archiving Conference, 2012
�User/ institutionally defined color weightings based
on a color importance strategy
�Supporting image analysis software
&target description files
Future Work
IS&T's Archiving Conference, 2012
• More census data• Metropolitan Museum of Art ?• Cornell University ?• Museum of Modern Art ?
• Patch selection refinements (v 0.2)• Metameric content?• Extended spectrally neutral grays• Fill color gaps• Reposition / Modify patches