I've never given this much thought before until it came up in the lengthy calibration thread. Rather than veer that thread (further) off-topic, I thought I would bring it up here. Someone posted an FFT of a master dark from an OSC camera. The FFT showed obvious regular patterns are present in the dark master. I replied that the FFT is almost certainly showing the bayer pattern. Since I do a lot of OSC imaging, I am used to seeing the familiar checkerboard pattern in undebayered images.
Then it occurred to me - darks should be blind to the bayer pattern. After all, the bayer array is an array of color filters over the pixels so there should be no evidence of the bayer pattern in frames exposed to no light. Yet there obviously is. I see it in all of my master darks for my OSC cameras. Darks should only show dark current artifacts and should be agnostic to the CFA, but they're not. So now I'm wondering why. Anyone care to enlighten me?