Wrong 2D plot of ProPhoto RGB with ColorThink Pro

I have just downloaded ColorThink Pro last beta 22 and I have noticed that ProPhoto RGB 2D gamut is still wrong (old bug). It should a simple triangle with imaginary primaries but it is not…

You dont get a triangle (as you get with ColorThink) but a “pseudo-triangle” with exotic curved sides. Why ?


Hi Jean,
I guess I’m not seeing what you’re seeing. With ColorThink 2 as well as with CTPro, ProPhoto graphs with its corners “cut off.” (I am including a screenshot of ColorThink 2 in 2D mode. CTP is similar except that the grid is enabled.)
Is this what you’re seeing?

The simplest explanation for this is that those imaginary colors are outside of the grapher’s ability to graph. Lab space is a cube of 128 x 128 x 100, and two of those ProPhoto primaries are outside of that range. That’s one big color space isn’t it?!

Hi Patrick,

I mean that xy 2D plot of ProPhoto is right by ColorThink but wrong by ColorThink Pro :

  • ColorThink plot is the right perfect triangle with summits at the right three ProPhoto primaries.

  • ColorThink Pro plot is wrong. It is not a triangle but a strange figure.

This bug is quite old. I noticed it in the first ColorThink Pro version. The funny plot should be now famous because it was given in an excellent paper about Lightroom when this software was first released…

Yes, using the Yxy coordinates, the 2D outline of the 3D gamut of ProPhoto does not match the gamut. The 3D gamut is correct, but the projection or outline of the 3D graph onto the base of the grapher is not drawing correctly with ProPhotoRGB. I don’t know the details of why this is, but it’s probably one of the reasons we’re not out of “beta” yet.

This persistent bug is now very old. ColorThink Pro plot wrong 2D xy gamut for ProPhoto RGB AND other wide gamut working spaces. Because of this bug, wrong plots can be seen in some papers published by famous experts…

I am very surprised it is not yet fixed.
What is your plan about it ? It’s now hard to trust ColorThink Pro plots…

Hi Patrick,

Have you got news about this old bug ? Is ColorThink Pro going to plot right 2D xy gamut for ProPhoto RGB ?
To make such a plot, we cannot anymore use standard version ColorThink 2.2 because it doesnt works with Seven 64 bits…

Hi Jean,

We’ll see what we can do. I fully appreciate the position you’re in, and we need to provide a solution for you somehow.

ColorThink v2.3 (non-Pro) for Mac and Windows is now available. This will allow you to use ColorThink 2 on the latest Windows operating systems. A series of updates brings full Windows 7 compatibility (32 and 64 bit), corrected rotation animation in the Grapher, and numerous other tweaks and fixes. This is a free upgrade for all current ColorThink 2 users.

Download here:

More information: