Hallöchen! Louis Granboulan writes:
> [...] > > [...] The viewfinder shows 100% of the picture, including the > corners, but there is almost no vignetting in the viewfinder. > Therefore this vignetting is mainly caused by elements that are > not between the subject and the main mirror… that's why my > conclusion is that it is pixel vignetting, caused by the depth of > the sensor pixels and the angle of the light reaching the sensor. You need oblique angles of incident light on the sensor to get noticeable pixel vignetting. At 60mm and 43mm sensor size, the angle is 70° (90° would be perfect). This should not be a problem for any sensor. Besides, a 60mm macro should have the same problem. That said, there are details (telecentric vs. entocentric comes to my mind) which I don't know very much about. > But whatever causes this vignetting, the thing is that the corners > are sharp, that's why I want to be able to compensate the > vignetting! I can understand that. >> Lensfun should work for all lenses, but this is really unusual. > > This is not so unusual: I have the same behaviour using the smc > 55-300 fully open at 300mm on the Pentax K-1. I've worked on sample images of 400 lenses and I've seen this very very rarely. At least for non-compact cameras. Actually, I only remember that Sony lens. >>> The coefficients above work well on this picture (using darktable) >>> but not on the TIFF. [...] >> >> Is the colour space linear RGB? You might try >> "dcraw -g 1 1 -T -W <DNG>". > > With the version of dcraw I am using, this command line fails to create a > valid > TIFF file, because the tags are not sorted in ascending order, but ImageMagick > can manipulate it therefore it might not be a problem. > And the correction with > convert IMGP4694.tiff -fx "Xi=i-w/2; Yj=j-h/2; > r=hypot(Xi,Yj)/hypot(w/2,h/2); s/(1-0.156*r^4-0.711*r^6)" > IMGP4694-corrected.tiff > does not give the same result as having > <vignetting model="pa" focal="250" aperture="4" distance="1000" > k1="0.0" k2="-0.156" k3="-0.711" /> > used by darktable The TIFF might contain a gamma curve, which thwarts vignetting correction. Instead, the colour space must be linear RGB. Tschö, Torsten. -- Torsten Bronger ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, SlashDot.org! http://sdm.link/slashdot _______________________________________________ Lensfun-users mailing list Lensfun-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/lensfun-users
