Targeting for Important Color Content: Near Neutrals and Pastels

Don Williams, Image Science Associates

&

Peter D. Burns, Burns Digital Imaging

Presented at the IS&T Archiving Conference, Copenhagen June 2012© copyright 2012 Don Williams and Peter D. Burns

Important Colors !

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Color Specificity ?- we can do better -

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Statement of the Problem- the wrong tool for an important job -

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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

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Design, build, and test a color imaging reference target more suited to the needs and color demographics

of cultural heritage imaging collections.

Execution

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� 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 -

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19th century photographic collection content from IPI

New Work - Color Census- beyond -

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New Work - Color Census- beyond photographic content-

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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-

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- 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

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Data Analysis- CIELAB coordinates from color census vs. candidate target -

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-60 -40 -20 0 20 40 60

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L*

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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 -

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�User/ institutionally defined color weightings based

on a color importance strategy

�Supporting image analysis software

&target description files

Future Work

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• 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

• Software enablement• Free analysis software• Target description file execution (CxF format)• Color profile execution

• Field Testing• Create test plans and identify partners• Distribute v 0.1 targets.