[teaspoon]

Are you talking about things like sensor noise and chromatic aberration? It would be interesting to see if downsampling the image beforehand affects the result.

However, it's hard to separate image patterns from camera structure insofar as linear projection is a result of camera structure.

[fridek]

I was thinking about CFA mosaic and JPG compression, I think these may introduce some axis aligned artifacts. But maybe they took it into account (using raw format?) or effect is not relevant in this case.

[trunnell]

Even in raw format, all digital cameras apply some amount of sharpening [1] even when the setting is "off" in the camera menu. Also, all raw format conversion software (Lightroom, Capture One, etc.) applies sharpening by default.

I could imagine that a sharpening algorithm could transform a random distribution into something with structure. That the authors appear to not reference camera or image sharpening anywhere in the paper is somewhat worrisome.

[1] http://en.wikipedia.org/wiki/Unsharp_masking