ilumo wrote in post #18154153
I was actually comparing some images of the 5dsR and the 5d4, and a thought came out... if the 5dsR applies a "cancellation" filter to get rid of the AA, is it possible to somehow replicate that in post for the 5d4, and i guess any other cameras that have an AA filter...
No; the cancellation is optical. Sharpening returns some of the pixel-level contrast lowered by the AA filter, but you can't get exactly what you would have without an AA filter in the first place. That is impossible, as the resolution frequency domain is soft-clipped by an AA filter, to prevent false resolution (mirror) frequencies from coming through.
The typical AA filter is two sheets of what are called a "birefringent" material (sp?), which takes a point of light and turns it into two points, their distance determined by the thickness of the material. Two sheets are laid down, at 90 degrees rotation, so each dot becomes 4 dots, like the corners of a square. When the filter is cancelled, the lower sheet is inverted so that it turns the two points back to one point, instead of 4. This way, the thickness is maintained and is consistent between the two camera designs. I have no proof, but suspect, that the cancelled type is actually better than having no AA filter at all, because it may turn that hypothetical dot into a slightly wider dot due to imperfections in the filter, but still quite small, which may attenuate the most egregious (mirror) frequencies, without reducing maximum pixel contrast by very much.