Hey Alex,

I know you are very brief in answering questions, but I'd love if you answer my questions. I'll make it bullet style and mark them in bold, so it's clear what my questions are.

First a bit of context: I want to know the XYZ coordinates of the camera primaries of the Bayer channels. I want to do this in a general way for both 3-component and 4-component color models. For now, I was using the cam_xyz matrix limited to the 3x3 submatrix in case of 3-component color data, and invert that to be able to convert Bayer primaries to XYZ. But that doesn't work for 4 components, as this matrix transforms the wrong direction for me.

• What is the most portable way across cameras and color models to obtain the XYZ values of the Bayer primaries?
• What is the use of the cam_xyz as this converts from XYZ to camera, and not the other way around? When is this useful?
• I have seen rgb_cam converts from camera to sRGB. If I use this, followed by converting this sRGB to XYZ, I'm where I want. However: I have seen you mentioned a couple of times here on the forum that cam_xyz_coeff produces rgb_cam. So I'm wondering: Where does this 3x4 matrix come from?

Many thanks!
Martijn