CTP3.0.2 : wrong 2D xy plot for ProPhoto, now for eciRGB too

Hi Patrick !

Before new 3.0.2 version, ColorThink Pro was unable to plot right 2D xyY gamut for large gamut color spaces. For instance, ProPhoto RGB plot was NOT un triangle but a strange figure, a pseudo-triangle with exotic curved sides. Remember my old post [one.imports.literateforums.com/t/wrong-2d-plot-of-prophoto-rgb-with-colorthink-pro/745/1)

Now, with 3.0.2, 2D xyY plot for eciRGB or eciRGB_v2 are also wrong ! I mean that they are no more triangles… I also tested Adobe RGB (1998) plot which is a perfect regular triangle (by luck ?).

So, this old bug is not only still alive but is now growing…

Do I make a mistake ? Any explanation ?

More hypothesis about this bug :

ColorThink 3 (version non-pro) makes a RIGHT 2D xy plot of ProPhoto RGB. For the same color space. But, ColorThink Pro makes a WRONG 2D Plot. So, I suppose that they follow two different ways to calculate the same gamut…

May be ColorThink 3 simply plots the triangle with three corners at the three primaries points… (If I had to plot such a gamut, I would do so…)

May be the more expensive ColorThink Pro is more courageous than its lazy non-pro brother. Perhaps this more sophisticated software built the 2D xy gamut plot from a projection on xy plan of 3D xyY volume plot. If my hypothesis is right :

A - projection algorithm may be wrong,
B- 3D gamut may be wrong.

Hi Jean,

You are correct. We were not able to fix your bug with this latest version of ColorThink Pro. While it may seem to be a simple fix, it turns out to be a very complicated issue. Fixing this bug requires changes to the software beyond the scope of what our software is capable of right now.

I believe your estimate of what ColorThink 2.3 (non-Pro) does is also correct. This is a much simpler program.

For those who want to see a 2D gamut projection in ColorThink 2, bring your images into the 2D Grapher, choose gamut colors, spectrum locus, etc to taste. Then, to get an outline of the gamut (not filled), click on an empty spot in the Plot Items field. The solid gamut will turn to outline.