right, this kind of artifact results from low bit depth even for perfect images without noise reduction. ulrich wrote the dithering module to counteract that:
http://www.darktable.org/usermanual/ch03s04s04.html.php#dithering might be helpful in your case, too. cheers, jo On Thu, Nov 12, 2015 at 3:08 PM, André Felipe Carvalho <afelipe.carva...@gmail.com> wrote: > This photo was saved in jpeg 100%, raw denoising of 0.004. I managed to get > rid of the majority of the bands, but you can see some lines above/around > the sun. > https://www.flickr.com/photos/andrefelipecarvalho/22536463868/ > > > > 2015-11-11 22:34 GMT-02:00 André Felipe Carvalho > <afelipe.carva...@gmail.com>: >> >> Hello Johannes, >> >> I was using Jpeg 97% >> >> I use, normally, only the raw denoising, starting with 0.002 points, going >> to 0.006 if needed and the image colors permit. >> >> Experimenting with 0.004 raw denoising I can see some band even with the >> PNG 100% export. But I admit it's better then at 97% jpeg. >> The bands, now, are narrower than before. Less visible at the orange sky >> parts and more apparent at the dark, silhouetted parts. >> >> Pulling the Color Balance first factor (Levantar, in portuguese) a little >> bit to the left may help to disguise the bands. >> >> Thanks again, >> André >> >> >> 2015-11-11 14:24 GMT-02:00 johannes hanika <hana...@gmail.com>: >>> >>> On Wed, Nov 11, 2015 at 11:05 PM, Tobias Ellinghaus <h...@gmx.de> wrote: >>> > Am Dienstag, 10. November 2015, 19:15:10 schrieb André Felipe Carvalho: >>> >> I've been experiencing this behavior specially in sunset photos. >>> >> >>> >> After applying the modules that I want, among them the sharpness >>> >> module, if >>> >> I want to get rid of the raw noise, the exported jpeg shows bands on >>> >> the >>> >> degrades parts of the image (sky, for instance, or dark areas). >>> >> The exported image without Raw Noise Reduction is about 6.8MB, while >>> >> the >>> >> one with noise reduction goes down to 2.8MB. Why's that? >>> >>> that's normal, noise has high entropy and doesn't compress as well as >>> the low noise one. >>> >>> did you only do raw denoising? or any non local means, too? any >>> wavelet based method shouldn't lead to as much banding as nlmeans >>> (because the latter uses a piecewise constant prior). >>> >>> -jo >>> >>> > >>> > - What is your "quality" setting in the export module? >>> > - Could you try exporting to PNG and see if that has the same problems? >>> > >>> >> The IQ is bad (because of those bands) and I have to turn noise >>> >> reduction >>> >> off. >>> >> >>> >> I can provide some samples, or the raw file and the .xml associated. >>> > >>> > Tobias >>> > >>> > ------------------------------------------------------------------------------ >>> > >>> > _______________________________________________ >>> > Darktable-users mailing list >>> > Darktable-users@lists.sourceforge.net >>> > https://lists.sourceforge.net/lists/listinfo/darktable-users >>> > >>> >>> >>> ------------------------------------------------------------------------------ >>> _______________________________________________ >>> Darktable-users mailing list >>> Darktable-users@lists.sourceforge.net >>> https://lists.sourceforge.net/lists/listinfo/darktable-users >> >> >> >> >> -- >> André Felipe >> ============================================ >> New beginnings are often disguised as painful endings. >> >> -------------------------------------------------------------------------------- >> Lao Tzu >> ============================================ > > > > > -- > André Felipe > ============================================ > New beginnings are often disguised as painful endings. > > -------------------------------------------------------------------------------- > Lao Tzu > ============================================ > > ------------------------------------------------------------------------------ > > _______________________________________________ > Darktable-users mailing list > Darktable-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/darktable-users > ------------------------------------------------------------------------------ _______________________________________________ Darktable-users mailing list Darktable-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/darktable-users
