Challenges > The Curvemeister Challenge

A Hue challenge - the answer, but what should we do?

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themightyzog:
I'm starting a new thread because the answer to the problem raises further questions that I would appreciate some discussion on and therefore hope that those that have already read the 1st thread will read this one.

I had a reply, on another Forum, which said:- "I had a look at sRGB and AdobeRGB spaces compared to my monitor's colour profile, the really saturated corners of red and green are the bits that poke out into the out of gamut areas. Possibly explains your inability to see changes deep into the pure red and greens."

Here are two bands of colour change, each by 6 degrees of Hue. The top one easily shows 6 hues and the bottom one 7. Changing to RGB, instead of this sRGB image, marginally makes it easier to see the green ones.

However, can anybody tell my why assigning no profile does not make it any easier - does this mean that displays are not very good at green?

It appears from my tests that the area 108-120 degrees of Hue are difficult to differentiate, but nature is full of shades of green, which I assume we can see, but screens (and printers?) can not show.

So does this mean that we need to apply the Man from Mars (or similar explosion) technique to this green area in order to display to the viewer what we photographed?

Greg Groess:
How do they print??

Just curious...

Greg Groess:
BTW when you select the text of the posting and include the images so there is a blue highlight over the image you can see some of the green steps...I am betting you are right it's the monitor....

Greg

jacobolus:
If this is HSL/HSV hue, the reason here is that those models are very simple transformations of RGB, designed to be fast to compute on computers of the 1970s, and have little relation to human visual perception.  CIELAB (L*C*h*) hue is reasonably perceptually uniform, but not ideal, and has some nasty curvature of perceptually constant hues as chroma increases, particularly in the blue/purple region.

To get perceptually uniform hue differences, look at your colors in a color appearance model like CIECAM02 (JCh).  Or in the Munsell color system.  Bruce Lindbloom has an ICC profile which sends CIELAB through a look-up table which warps it to match up to the Munsell renotation data; that should work better than just normal CIELAB for getting perceptually uniform hues.

Short answer: HSL/HSV are stupid color models to use in 2008, now that computers are fast.

You may find this article (I never finished writing) useful: http://en.wikipedia.org/wiki/Munsell_color_system

jacobolus:

--- Quote from: Greg Groess on April 05, 2008, 10:08:55 PM ---BTW when you select the text of the posting and include the images so there is a blue highlight over the image you can see some of the green steps...I am betting you are right it's the monitor....
--- End quote ---
I can perceive all of the color steps on a properly calibrated display (if I look very closely; I also have pretty decent young-person’s eyesight).  But no, the reason for the difference between the two hue gradients here is not the display.

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