Problems measuring camera SNR with darktable and Raw Therapee

[heckflosse (Ingo Weyrich)]

@garagecoder

Looks like something periodic happening and not exactly aligned with your 200x200 grid (need to click and view full image to see that properly).

Amaze demosaic processes the images in tiles of size 160x160. But I would not expect this causes the issue, as darktable amaze code uses the same tile size.