Forgot a third reference: EXIF tags for Sony cameras (read by exiftool) [3] http://www.sno.phy.queensu.ca/~phil/exiftool/TagNames/Sony.html
On Tue, 4 Apr 2017 at 22:33 Kelvie Wong <kel...@kelvie.ca> wrote: > Hello all, > > I just realized that on my Sony a7R II (and this probably applies to all > of the cameras in this series, probably even the NEX), if you have certain > camera settings, some lens corrections are baked into the ARW files (Sony's > raw format) -- that is the bit values appear to change, not just the > metadata. > > I've been doing some experiments with my lenses as I have been calibrating > them for lensfun (and now may have to re-do the TCA corrections). > > The two corrections affected are vignetting corrections (Sony calls this > Shading Compensation), and CA corrections. > > This means that when lensfun applies the corrections, they could be > applying them twice if the camera had already applied them to the raw. > > Now, in an ideal world, we would instruct the user to always turn these > off, and apply lensfun corrections once, but perhaps an even better > approach would be to have the lens correction module *not* apply TCA and > vignette corrections depending on whether or not the EXIF data says it has > already been applied. > > 0x2011 VignettingCorrection (uint32); 2 = auto, 0 = off > 0x2012 LateralChromaticAberration (uint32) 2 = auto, 0 = off > > 0x797d LightFalloffParams int16[17]; first integer seems to be 16 if this > is a supported lens with vignetting data, 11 when using a legacy adapted > lens (possibly a bit field?) > 0x7980 ChromaticAberrationCorrParams : exact same as above > > So the criteria would be: > > if (VignettingCorrection == 0 || LightFalloffParams[0] != 16) > applyVignetteCorrections(); > > and similar for CA. > > An even more advanced approach would be to parse those values, undo them, > and apply the lensfun data, as the in-camera corrections don't seem to be > enough to get rid of the light fall off and CA as well as lensfun data does. > > Distortion correction doesn't seem to ever be applied to the ARW file > (just the JPG), so we can always apply those. > > Anyway the main question is, I can code this; but does this belong in > lensfun, rawspeed/libraw, or darktable's lens correction module? > > References: > [1] > http://www.sonyalpharumors.com/the-big-sony-test-in-camera-lens-compensation-by-jorg-haag/ > [2] > https://diglloyd.com/blog/2015/20150527_0544-Sony-lens-corrections.html > > P.S. Sorry about the formatting, I typed this in gmail. I can reformat if > needed. > -- > > -- > Kelvie Wong > -- -- Kelvie Wong ___________________________________________________________________________ darktable developer mailing list to unsubscribe send a mail to darktable-dev+unsubscr...@lists.darktable.org
