So, Steve, anything that is outside of that "1 Lab" unique cube is considered a "different color", in ColorThink? Is that your criteria? / Roger -----Original Message----- From: colorsync-users <colorsync-users-bounces+graxx=videotron.ca@lists.apple.com> On Behalf Of Steve Upton via colorsync-users Sent: Tuesday, January 7, 2020 3:59 PM To: colorsync-users@lists.apple.com Subject: Re: 1 billion colors
On Jan 6, 2020, at 1:36 PM, Roger Breton via colorsync-users <colorsync-users@lists.apple.com> wrote:
Well, Andrew, just to push the discussion further, I would *love* to hear what Steve Upton would have to say about “unique colors” since he’s the one that wrote the application: what numerical criteria does Steve use in ColorThink to distinguish among “unique colors”?
Gah! I've been drawn into the angels-on-the-head-of-a-pin discussion again! I agree with all of you... does that help? I have to admit the "There's a color missing, prove me wrong" is pretty damn funny. Good to get a chuckle from this stuff sometimes. My 2 bits? There's an interesting point here about the difference between addressable colors and addressable unique colors. For me (not necessarily using the correct terms) an addressable color in this discussion would be any RGB value that results in a Yxy value that falls within the chromaticity diagram and represents an actual, visible color. This includes any precision level so imaginary 128bit-per-channel RGB spaces would be included as well. There'd be a lot of wasted bits addressing imperceptible color differences but they'd be real colors. This brings me to: Addressable *unique* colors is the idea that perceptual spaces like Lab have a kind of maximum resolution, where we could use a set of coordinates that is no more precise than our ability to see the differences between colors. Each unique color is effectively assigned a coordinate and we're good to go. "But wait", you might say, "color perception is analogue and infinitely variable" (nod to Mr Gnaegy, good to hear from you sir). "A hard-edged coordinate system could never capture it!" I agree that we're analogue beasties but it's not a problem. In our discussion we're talking about trying to address unique colors. If we use such a hard-edged coordinate system there's nothing saying it can't be slid around / re-aligned with infinite precision, only that the differences between the coordinates would need to remain the minimum perceptible difference between colors - therefore it still addresses unique colors... If I understand and slightly warp the intentions of our color forefathers properly, CIELAB was intended to be just such a coordinate system, where 1 unit of movement in any direction would be the human perceptual limit of color change. If you added up the "volume" of such 1-unit cubes in a defined area, such as a printer gamut, then you'd have a number representing the number of unique colors available. That's exactly what I do in ColorThink. Unfortunately CIELAB is flawed, or perhaps it's better to say that human color perception doesn't adhere to such a simple model. Newer models have been created such as CIECAM that help address some of these limitations. Suffice to say that there's broad agreement that CIELAB and delta-E 76 are dangerous to use naively, yet remain quite useful and delta-E 2000 helps bring color differencing numbers more in line with human perception. Though I recognized that the concept of a total gamut volume is disputable and somewhat flawed from the start, I thought that it probably still had value and chose to include it in ColorThink Pro. At the very least I thought it would start some interesting discussions! Overall, I think it has been useful, especially in a comparative sense. Are there better ways of doing it? Undoubtedly. Is there agreement on which ways are better? Not much that I can find yet, but work on the science continues and we continue to learn as we go. Those who are attending the Color20 Conference in San Diego next week will be treated to a sneak peak of what's coming in ColorThink 4 later this year - like new color spaces for graphing, advanced gamut comparison functions, and so forth. regards, Steve _______________________________________________ Do not post admin requests to the list. They will be ignored. colorsync-users mailing list (colorsync-users@lists.apple.com) Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/colorsync-users/graxx%40videotron.ca This email sent to graxx@videotron.ca