

Color Spaces for Human Beings (2012) - mrzool
http://www.boronine.com/2012/03/26/Color-Spaces-for-Human-Beings/

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foolrush
And they get it wrong right out of the gate.

There is a distinction between a colour encoding model and a colour space.

RGB is a relative colour encoding model, not a colour space.

More poorly written misinformation to keep confusing the “humans.”

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jacobolus
I’ll agree that “color space” isn’t the most useful term because it’s pretty
vague, but there’s really not a meaningful “distinction between a color
encoding model and a color space”, sorry; “color encoding model” isn’t a
standard term, and is also not very descriptive. Moreover, “relative color
encoding model” isn’t a term used by anyone ever and doesn’t have a prima
facie obvious definition, so nobody is going to understand precisely what you
mean by it.

I’d rather see terms like “color appearance model” or “color order system” or
“device-dependent color space” etc., but using vague generic terms is
occasionally appropriate, so we shouldn’t totally chuck them out.

In any case, such semantic quibbling is all fairly irrelevant to anything, and
has very little bearing on whether the page under discussion is
“misinformation”.

~~~
foolrush
RGB is a colour model.

It is misinformation.

The reason that a given HSL / HSV implementation may not accurately deliver a
given chromaticity vector has more to do with the nature of colour spaces than
the model's implementation implicitly.

So I disagree, it is misinformation, and the reasons for choosing a given
color model / colour encoding scheme are varied.

An incorrect and simple answer for a complex series of problems.

~~~
jacobolus
Sorry to sound negative here, I’m not trying to discourage you. You seem to
have a bunch of misconceptions about color and color science. My primary
recommendation is to try reading a couple books about the subject, which
should help you get a better grip on the parts you’re currently missing.

> _RGB is a colour model_

Without some further qualification, “color model” and “color space” are
effectively synonyms.

> _It is misinformation._

There’s really nothing particularly wrong with the linked article. I don’t
like the author’s proposed HUSL space, but his explanation of why HSL and HSV
are bad tools is straightforward and reasonable.

> ... _a given HSL / HSV implementation may not accurately deliver a given
> chromaticity vector_ ...

In a technical sense, “chromaticity vector” is not very meaningful as a term
when discussing gamma-corrected RGB coordinates, and is _completely
meaningless_ w/r/t HSL or HSV. Chromaticity is a precise technical term,
referring to the projection of trichromatic matching functions onto a two-
dimensional plane perpendicular to luminance. When people talk about
“chromaticity” they usually either mean xy coordinates in xyY space, or
sometimes u', v' coordinates, or very occasionally some other chromaticity
plane, such as more recent spaces based on more explicit measurements of human
cone responses. The Cr and Cb coordinates of a Y'CrCb model are sometimes
referred to as “chromaticity” coordinates, but in a technical sense that is a
wrong and misleading term to use.

I’m not sure what “given chromaticity vector” you are talking about, but if
you want to get chromaticity from R'G'B' values, you should first linearize
them, then transform from RGB -> XYZ, and then divide by Y to find x and y.

> ... _has more to do with the nature of colour spaces than the model 's
> implementation implicitly_

This is not a comprehensible string of words. I’ve spent more than a decade
studying color science, color reproduction, etc., and I don’t have the
foggiest idea what you’re getting at.

~~~
kelsolaar
Thanks for that, terminology is important in any domain but I found it to be
decisive when you talk about colour science. A lot of people are using
incorrect terms in incorrect contexts which leads to even more confusion.

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jacobolus
My comment about this from last week:
[https://news.ycombinator.com/item?id=9713814](https://news.ycombinator.com/item?id=9713814)

