The first point is the most important, it is common with open source raw editor to apply geometric lens and perspective correction before sharpening.
We should keep in mind that in this way we are add to the picture a lot of arifacts likes ringing, haloes, aliasing and so on before sharpening, in the case of a noises image we are sharpenng noise and interpolation artifacts.
Wouldn’t be better for a cleaner image to move geometric lens correction and perspective correction at the end of the toolchain pipeline?
The second point (question) is related to the tone manipulation, where is the more appropriate place to sharpen? After denoise and before any kind of tone manipulation (filmic,curve,…) like darktable?
Or after denoise and after tone manipulation like rawtherapee?
I have the impression that sharpening before is actually sligthly less effective but a little more cleaner
To compensate for in-camera anti-alias filter, so the pixel values are closer to what an ideal camera would capture.
To prettify the picture, as part of a “look” transformation. This sharpening may depend on the intended purpose, eg printing, or web-sized images.
If we confuse these two purposes, we are asking for trouble.
Geometric lens correction corresponds to (1). It compensates for pincushion etc distortions. Personally, I rarely do this because (a) my lenses are quite good and (b) the distortions rarely matter. More importantly, for me, is chromatic aberration, which I correct before demosaicing. Likewise noise, when I care about it.
