Hello Dennis, I think you have resolved a unspoken wish of mine for darktable :)
I have several old lenses (up to 60 yrs old), one of them is a 200/3.5mm which I always use with a 2x TC. As one can imagine, the resulting CA is quite significant and I couldn't eliminate it with the existing CA-module. I thought that it is too heavy that for dt to detect it, but after reading your 2 mails I think it was the fact that it isn't geometrically centered, but is heavy at the center itself. I hope I can test it at the weekend with different pictures (e.g. a lonley bird in front of the sky, wich may be a problem for the detection algorithm?) and give you feedback. If you don't hear anything from me, please just remind me :) regards, sebastian On 10/22/2013 01:55 AM, Dennis Gnad wrote: > Hi, > > On 19.10.2013 20:40, Torsten Bronger wrote: >> [..] >> I recently bought a Samyang 500/6.3 mirror tele. It suffers from >> significant LCA. I have uploaded RAWs here: >> https://bob.ipv.kfa-juelich.de/bronger/lca/ > Thanks for trying it out and for the example pictures! > > Just if you are interested and want to see something really horrible > with both TCA and LCA (a white statue in the bright sun at f1.8): > http://xorn.org/darktable/DSC_1061.NEF > > What would be interesting for me, maybe you can take one more shot which > shows some LCA and still has a bit more different colors in the picture > if possible. Selectively desaturating the *right* parts can be a > problem. I might also try to make some more pictures myself, > specifically for benchmarking -- I probably don't have the best > selection at the moment. > >> The module works well but I have to set "threshold" to the minimum >> always. Furthermore, I set the green/magenta slider to the far >> right, and the "blue/yellow" slider to the far left. After all, the >> short wavelengths are the problem. > Ok, as far as I understood (correct me if I am wrong) in general LCA > (Longitudinal/Axial CA) can be different colors (mostly green or > magenta), as any wavelength can be affected by being at one side of the > out of focus regions. I read > http://wiki.panotools.org/Chromatic_aberration and > http://blogs.adobe.com/lightroomjournal/2012/04/new-color-fringe-correction-controls.html > > - though they seem to use the terms a bit different, but it seems to be > as follows: > > Longitudinal CA = Axial CA = LCA > Lateral CA = Transverse CA = TCA > > What I want to remove is the wavelength dependent focal length (LCA) > issue that Adobe describes like: > "Fringes typically appear purple/magenta when they’re in front of the > plane of focus, and appear green when they’re behind the plane" > > In the panotools wiki they say "You would have to focus differently for > red, blue or green.", where I first thought that it might be better to > work on RGB instead of Lab space. > > Maybe a slider between only purple and green would be better, or a green > strength and purple strength. That would also increase ease-of-use. > > I probably still need to experiment a bit further, let's see if I have > enough time to get this in the next release, or only after it... > > Best regards, > Dennis > > > > ------------------------------------------------------------------------------ > October Webinars: Code for Performance > Free Intel webinars can help you accelerate application performance. > Explore tips for MPI, OpenMP, advanced profiling, and more. Get the most from > the latest Intel processors and coprocessors. See abstracts and register > > http://pubads.g.doubleclick.net/gampad/clk?id=60135991&iu=/4140/ostg.clktrk > _______________________________________________ > darktable-devel mailing list > darktable-devel@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/darktable-devel >
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------------------------------------------------------------------------------ October Webinars: Code for Performance Free Intel webinars can help you accelerate application performance. Explore tips for MPI, OpenMP, advanced profiling, and more. Get the most from the latest Intel processors and coprocessors. See abstracts and register > http://pubads.g.doubleclick.net/gampad/clk?id=60135991&iu=/4140/ostg.clktrk
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