Hi,
I've noticed that ppg and amaze demosaic create a kind of structured
patterns. The patterns very pronounced with high iso images ceating color
blotches and denoising profile on color causes unpleasant green spikes in
the image.
I've coded a simple staggered nearest neighbour interpolation demosaic and
it seems to perform better than dt 1.5.2 I checked out of git. Less
artifacts/patterns, color noice is more fine grained and profiled denoising
works better. Sharpness is of course less but for high iso this is very
reasonable. Here is a dropbox link to a 200% screenshot in my patched
darktable-master.
https://www.dropbox.com/s/l2vquxfu93cm5xs/Screenshot%20from%202014-02-18%2010%3A04%3A03.png
I've noticed there are special demosaic algorithms in literature which no
doubt are sharper and more advanced than my simplistic algorithm. In any
case I wondered if ppg and amaze are less suited for high-iso noise and we
might benefit from dedicated noise-capable demosaic code and would
appreciate a wider range of demosaic code.
Best,
Gert
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