2

Initially, using RGBColor, I assumed that it accepts values in sRGB color space. But when I started doing calculations and conversions between various color spaces, I noticed quite large differences from my "manual" calculations. Then I tried to use ChromaticityPlot and check my assumption. Here's what I got:

ChromaticityPlot[{"sRGB", "RGB"},
 PlotPoints -> 171,
 PlotRange -> {{0.14, 0.7}, {0.05, 0.61}}
]

chromaticity plot

Obviously, the two color spaces are different, but I can't seem to find any information on what exactly this "RGB" color space stands for.

So, what does this RGB stand for? Is it some standard color space? What are its specs – gamma etc.?

J. M.'s missing motivation
  • 124,525
  • 11
  • 401
  • 574
Ruslan
  • 7,152
  • 1
  • 23
  • 52
  • I do not have Mathematica right now, but last I looked into this, one is a gamma-corrected version of the other, and one is using either of D50 or D65 as the white point. Have you seen this? – J. M.'s missing motivation Oct 14 '18 at 01:27
  • @J.M.issomewhatokay. they are both gamma-nonlinear, and seem to have very close gamma values. Actually that QA thread does answer my question: RGB is D50-chromatic-adapted version of sRGB. Seems chromatic adaptation somehow alters the primaries in addition to white point. – Ruslan Oct 14 '18 at 07:16

1 Answers1

1

It seems to be the ICC profile your display is using or something very close to it. If I drag and drop the system file

/Library/ColorSync/Profiles/Displays/iMac-07570D0F-8B98-38D9-F3B5-3E817CAA82D0.icc

into an input cell, I get

icc

which when plotted with "RGB" looks as follows.

ChromaticityPlot[{"RGB", display}, PlotPoints -> 100, PlotRange -> Automatic]

plot

m_goldberg
  • 107,779
  • 16
  • 103
  • 257
  • Doesn't seem plausible. First, your primaries are quite different from those in the ICC profile. And second, I've tried checking the primaries on two different machines with different monitors and corresponding installed ICC profiles, but the results were all the same. Is your output of e.g. FullForm@ColorConvert[RGBColor[0, 1, 0], "XYZ"] the same as mine, XYZColor[0.385065, 0.716879, 0.0971045]? – Ruslan Oct 13 '18 at 22:50