Thursday, November 4, 2021

If CIECAM is the answer, what was the question?

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Imagine, while studying in preparation for his next life as a color scientist, the ghost of Alex Trebek visits us in his former role and announces his truly Final Jeopardy answer:



The contestants blink and Trebek explains:

“If CIECAM is the answer, what was the question?”

And the contestants answer:


Contestant 1: “What model predicts symmetric color matches?” WRONG: That was CIEXYZ.

Contestant 2: “What model predicts asymmetric color matches?” WRONG: That was CIECAT.

Contestant 3: “What model predicts color difference?” WRONG: That was CIECAM-UCS.

Contestant 4: “What model allows a stimulus, in given viewing conditions, to be numerically described with correlates of perceptual attributes such as brightness, lightness, colorfulness, chroma, and hue?” [1] CORRECT: Although CIE’s color-appearance models, CIECAMs, are not the only possible models.


Contestant 2: “That’s not fair! I’ve seen CIECAMs tested by asymmetric matches, but never by the elusive ‘numerically described perceptual attributes.’”


Contestant 3: “Well, come to think of it, Luo et al. [2] describe experiments to test people’s ability to use particular perceptual attributes: ‘For the memory matching method, observers are first trained using the Munsell colour order system (or some other suitable system) until they are very familiar with these scales (i.e., Munsell Value, Chroma, and Hue) … In the magnitude estimation method, observers are asked to make estimates of the magnitudes of some perceptual attributes (e.g., lightness, colourfulness, and hue). It is essential that each observer clearly understands the perceptual attributes being scaled.’”


Contestant 2: “It sounds as if those experiments tested the memorability and amenability for scaling of particular coordinates of a particular color-order system. They cannot make a statement about color appearance independent of the color-order coordinates chosen for training the subjects. How do you know one CAM is better than another if the subject’s training has such a bias? And I understand the precision of these tests is pretty low. I still think there is no match-free way to test a CAM—or for that matter, to use a CAM for color management. Alex is wrong and we should have a recount.”


Trebek: Well, it’s time for me to go now. This discussion is turning into a quagmire, and it looks like real color-management systems rely on asymmetric match predictions anyway. So let’s ask a professional organization like the ISCC to sort it out. Meanwhile, I’ll have to tell my game-show successor that the right question for CIECAM is “What color-management model is not out of Jeopardy?”


[1] M. D. Fairchild and L. Reniff, A pictorial review of color appearance models, 1997 SID/IS&T Color Imaging Conference, first paragraph of Introduction.

[2] M. R. Luo et al., Quantifying colour appearance part I. LUTCHI colour appearance data. Color Res Appl 16: 168-180 (1991).


Michael H. Brill


Tuesday, August 17, 2021

Color-Coding the Pandemic


Michael H. Brill, Datacolor

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Each of us has a different life story through the pandemic. My story does not include the uneasy “new normal” experienced by students in school. Part of the “new normal” requires students to attend school in staggered part-time schedules. How did kids react to this complication? In curiosity, I Googled my old high-school newspaper, the Brentwood Pow Wow. (Yes, the Native American name remains.) Immediately a web page appeared with an article for their April Fools’ edition: “Satire: Crayola Box Plan to Replace Original Tri-color Hybrid Plan;” author, Lilian Velasquez; dateline, 24 March 2021. This was going to be about color coding, about the resilience of young people, and maybe more.

The school had seen fit to illuminate the monthly calendar with color-coded parts to clarify three alternative student schedules. That was the original Tri-color plan. Ms. Velasquez started with a calendar illustrating the Tri-color plan (using the first three entries on the list below), and then “sprinkled in” the rest:

Teal: Fully remote students  
Gold: Hybrid students attend school on Tuesday and Fridays, and alternating Wednesdays.
Green: Hybrid students attend school on Monday, Thursday, and alternating Wednesdays.
Chocolate: Attend school 9 times a year, on the first Monday of each month.
Cherry: Attend school every day for only 4 hours each day from 9 a.m. to 1 p.m.
Magenta: Attend school only on Fridays for 16 hours.
Indigo: Attend school on the weekends from 7 a.m. to 2 p.m. (Saturday and Sunday)
Silver: Attend school twice a month on the 7th and on the 21st.

Velasquez then showed a typical one-month calendar annotated with a delightfully confusing panoply of font colors: a scheme that might give new meaning to the term “drop-out colors.” It’s the kind of gentle extrapolation one expects from high-school students in an April Fools’ satire. I remember reading such extrapolations and writing them. The genre was grounded in acceptance of the normal. Now it is the “new normal.”

Before I went to Russia in 2008 to teach English as a Second Language (ESL), I heard that Russians would characteristically respond to a story of complaint and indignation by declaring, “It is normal.” My trip confirmed that assertion. I think that every time we reset the condition that we consider normal, we rewrite the past to conform. It is a coping mechanism, and it is helped along by writers.

In the same vein, Jorge Luis Borges said: “Every writer ‘creates’ his own precursors. His work modifies our conception of the past, as it will modify the future.” The better the writer, the more responsibility this incurs.

Still, the past is not easily erased. Brentwood High School retains Native American metaphors. Our media preserve other metaphors, as does our collective memory—sometimes unconsciously. Borges himself, with his quote, immortalizes his own present (and our recent past) by using “his” instead of “their” in describing a hypothetical writer.

It is a delicately balanced narrative into which Ms. Velasquez entered as she wrote extrapolating a color code for the “new normal.” She writes well, and her underlying optimism can encourage us all. I wish her the best as she extrapolates further—we hope from a better “new normal.”

And perhaps her new color code foretells a career as an artist or color scientist!

Michael H. Brill
BHS Class of 1965