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I'm not sure this is the right place to ask, but is anyone aware of a metric for apparent chroma?

Now I understand that "chroma" and "chrominance" are very overloaded terms, so to clarify, I specifically mean the chroma described here--the "colorfulness relative to the brightness of a similarly illuminated white". At full saturation this should be 255. At any black/white/gray it should be 0. And the closer a lightness is to the ends of the spectrums, the lower the maximum chroma (in contrast to the inverse of saturation where it is always 255). Basically chroma is the lateral dimension of the HSL bicone.

Unfortunately, this color model makes no corrections for perceived chroma--that is, how our imperfect eyes perceive equal chromas differently based on hue (e.g. #FFFF00 does not appear as chromatic as #0000FF).

So my question is, is there such a metric? Or can anyone point me to an academic paper on the subject? My own searches have turned up nothing, not helped by the multiple definitions of "chroma".

For the curious, my objective is to establish a general approximation of "jarringness" for colors of text and backgrounds of websites, working on the theory that apparent chroma is a significant factor.

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  • As this appears to be an "individual perception" question I'm not sure that a useable metric could be developed as each individual would have differences in perception (both optically based on current condition of their eyes - astigmatism, various degrees of color blindness, etc.) and cognitively.
    – lawndartcatcher
    Jan 7, 2013 at 20:32
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    But there is a generalized understanding of the human eye's ability to perceive various points on the light spectrum. This is a great question, though so academically narrow in focus I'll be surprised if a usable answer arises.
    – plainclothes
    Jan 7, 2013 at 21:00
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    It's not quite what you're asking for, but I've seen efforts to get a quantifiable measure of perceived lightness and darkness of colours, like what Photoshop uses in Convert to Grayscale making greens lighter than equivalent reds. Here's an article on it - alienryderflex.com/hsp.html. I'm sure an equivalent for saturation is possible. The science of objectively measuring subjective perception is called psychophysics, might be a good place to look.
    – user56reinstatemonica8
    Jan 8, 2013 at 12:28
  • Also, consider asking at the Cognitive Science stack exchange site. They should be able to advise on whether there's good baseline data on perceived chroma which could get you started.
    – user56reinstatemonica8
    Jan 8, 2013 at 12:33
  • @user568458: That's "luminance" and is similar to what I was asking :)
    – 0x24a537r9
    Jan 8, 2013 at 18:18

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Ah, after some more searching, I found it on my own! It appears I was specifically looking for Munsell chroma, CIELAB LCH's chroma, or UP Lab chroma (all basically attempts to get at the same idea).

Unfortunately, converting between sRGB and Munsell chroma is non-trivial and UP Lab chroma copyrighted, but it looks like sRGB -> LCH is not too difficult.

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