displaycal version 4 icc profiles are not supported

Displaycal version 4 icc profiles are not supported software#

The new tristimulus values for the red, green, and blue primaries are placed in the 3×3 matrix for the display profile. (Keep in mind that a display will rarely be calibrated to exactly D50, so a chromatic adaptation transform will be applied to the measured data even for a small deviation from D50.) In simple terms, the chromatic-adaptation transform changes the tristimulus values of the red, green, and blue primaries to produce a D50 white from the sum of the three primaries. If the white point of the actual display is not D50, then a chromatic adaptation transform must be applied to the measured data to force the 3×3 matrix to deliver the CIE XYZ tristimulus values for D50. To be compliant with the ICC specification, the 3×3 matrix must deliver the CIE XYZ tristimulus values of D50 for the CIE XYZ tristimulus values of white (i.e., white XYZ for the display profile = CIE D50 XYZ). By following the rules of linear algebra, the sum of each row in the 3×3 matrix produces the CIE X, Y, and Z tristimulus values for the white point of the display (i.e., the sum of the top row delivers the X value, the sum of the middle row delivers the Y value and the sum of the bottom row delivers the Z value). When the display profile is based on the matrix structure, rather than the LUT structure, the 3×3 matrix contains CIE XYZ tristimulus values for the red, green, and blue primaries. I will focus on an ICC display profile for a color monitor as an example. That extra step was the application of a chromatic adaptation transform. That worked well for output profiles (e.g., printer profiles), but it created an extra step in the creation of display profiles (e.g., monitor profiles) and RGB color-space profiles when the native white point was not D50. Therefore, all the color coding in the PCS had to have a white point of D50. The ICC had specified CIE D50 for the white point of the Profile Connection Space (PCS). Let me back up and give you a little more context for this issue.

Displaycal version 4 icc profiles are not supported software#

At the time, the International Color Consortium (ICC) did not specify a chromatic adaptation algorithm, so each software developer could choose any method for chromatic adaptation. When I was working on improvements to the OptiCAL software in 1998, one of the challenges was the selection of the chromatic adaptation algorithm.