Gonçalo Marrafa <goncalo.marr...@gmail.com> writes: > Hi. > > DT has two distinct modules for CA correction.
It actually has at least three : * "chromatic aberration" works only for RAW (only Bayer sensors), and has no setting: it just guesses the CA and tries to fix it. In my experience, it works only for very light CA. * TCA correction in "lens correction". This one uses a lens database (lensfun) and knows what the TCA of your lens is from this database. It applies the reverse transformation to realign the color channels. In my experience, this is the best option if your lens is known (and otherwise, have it calibrated: http://wilson.bronger.org/calibration) This module comes after "chromatic aberration" in the pipeline, so activating both is usually not a good idea, you may overcorrect the aberration. * "defringe" is new in dt 1.6. It does not know the caracteristics of your lens, and does not even try to guess it: it just looks for color fringes and desaturate them. If you have a picture of a sharp black/white edge, your uncorrected picture will show e.g. black->red->white, and defringe will convert this to "black->neutral grey->white", which is not as good as realigning the colors channels. But "defringe" comes after the other two in the pipeline, so enabling "lens correction" and "defringe" makes perfect sense: first try to realign the channels, and if there's a remaining aberation, eliminate it with "defringe". As Markus already noted, defringe is more general than "lens correction" since it can remove any colored fringe, not just the TCA. Compared to "chromatic aberration", another advantage is that it works for any kind of images, not just RAW. The default setting works well, but you can fine-tune the parameters with "defringe". In short, I use "lens correction" with TCA correction on 99.9% of my pictures, and use "defringe" whenever the result is not 100% satisfactory. -- Matthieu Moy http://www-verimag.imag.fr/~moy/ ------------------------------------------------------------------------------ One dashboard for servers and applications across Physical-Virtual-Cloud Widest out-of-the-box monitoring support with 50+ applications Performance metrics, stats and reports that give you Actionable Insights Deep dive visibility with transaction tracing using APM Insight. http://ad.doubleclick.net/ddm/clk/290420510;117567292;y _______________________________________________ Darktable-users mailing list Darktable-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/darktable-users
