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I'm interested in comparing the camera readable chrominance change to what a person can actually see.

Are there any colors that result in a physical / measurable change in chrominance, but are invisible to the human eye?

4:2:2 and 4:2:0 compression settings take advantage of this human physiology for example.

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I believe MacAdam Ellipses would shed some light on what you're looking for.

Another link which also contains a graphical representation: http://www.kurabo.co.jp/el/world/en/room/color/page1_3.html

Long story short: changing color X by "percentage" a can cause it to be perceived differently, while changing color Y by the same percentage would not.

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  • This is fantastic. I'm looking for the Y's that offer the greatest range of non perceived color values. If I'm reading the link correctly, green is the color that has this. I need to get a list of the technical color values that constitute those 2 and 3 step ellipses. – goodguys_activate May 19 '16 at 19:54
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    It gets a bit more complicated. For example, the green area are the top with the big ellipse is well outside the sRGB gamut that normal monitors are able to display. Then, considering two very close colors that are indistinguishable on your calibrated monitor, it might just be that someone else's monitor which is (way) off, in a manner you can't predict, displays them sufficiently distinct. – D. Jurcau May 19 '16 at 20:26
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Are there any colors that result in a physical / measurable change in chrominance, but are invisible to the human eye?

Yes, imaginary colors. These are colors that we can describe by numbers, but are not present in color gamut of human vision.

... when I edit in photoshop, does altering a color X by percent Y have the same perceived / psychological effect on a human, or does it not?

Yes, if you are editing in perceptually uniform color space.

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  • Rather, when I edit in photoshop, does altering a color X by percent Y have the same perceived / psychological effect on a human, or does it not? I'm asking various forms of this question in different ways over SE in order to write an app that transmits data in this invisible channel – goodguys_activate May 19 '16 at 13:44
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    Altering X by percent Y has the same perceived effect only if you do your editing in perceptually uniform color space. – MirekE May 19 '16 at 21:24
  • This answer is inaccurate. All of the gamut of ProPhoto is visible to the human eye. – R Hall Jul 20 '16 at 1:08
  • ProPhoto RGB is a container space. Digital cameras render sensor information into it. Sensor information on digital cameras today do not get rendered into the portion of ProPhoto that is outside XYZ. MacAdam's work is relevant to this question, in that it shows color difference in the visible spectrum. – R Hall Jul 21 '16 at 13:25
  • Problem here, is there are no colors in this area, you can not print them or display them, so why answer, then argue this point. Done. – R Hall Jul 21 '16 at 23:08

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