Dear All, I've posted a few versions of an image on the darktable-users list that show that with dt 1.6.1 (from the 'stable' Ubuntu PPA) the shadows and highlights tool set to shadows = -100 (and, as it turns out, highlights = -100), combined with a large radius and small compression will *lighten* parts of an image, which seems to be contradictory with what the manual says, and also quite counter-intuitive. The guidance I received on the users list, including Robert Huttons great video tutorials, have been useful in general, but don't answer the specific questions.
Please don't take this double-posting as whining or complaining aggressively, I'd just like to learn about dt. I'd like to know: - is this a bug or a feature? If it's a feature, I'm happy with it, it has given me an effective way to bring out shadow details (create two instances of shadows/highlights, set one to shadows = -100, highlights = 0, the other the other to shadows = 0, highlights = -100; set both to compress = 0, radius = 200, merge: uniformly in lighten mode); if a bug, I won't rely on it; [a single instance, with both set to -100, does not work, it darkens the image as expected] - if a feature, the geek in me would like to know why this happens. It turns out that shadow > 0 can also darken some parts of the image (which, again, is quite counter-intuitive and against what the manual says). The example for darkening with shadows > 0 is: http://photos.kovacs-telekes.org/Other/Darktable-issues/Shadowshighlights20140105/i-MTZ7RR7/0/O/05-eye_closeup_radius40_compress20.jpg http://photos.kovacs-telekes.org/Other/Darktable-issues/Shadowshighlights20140105/i-Qgn2vJc/0/O/06-eye_closeup_without_sh.jpg In Gimp, using the colour picker with a 'sample average' of 10 at coordinates [680;545] (corner of the eye) I get (R, G, B) pixels = (134, 94, 80) for the '06-...without_sh' image and (129, 90, 76) for the 05 (sh enabled) image. For lightening with shadows < 0 is: http://photos.kovacs-telekes.org/Other/Darktable-issues/Shadowshighlights20140105/i-Nm3bJHh/0/O/08-eye_closeup_radius40_compress20_shadows-100.jpg Again, in Gimp, you can compare the brightness of the blemish (birthmark) above the eye between 05 (sh disabled) and 08 (sh enabled with shadow = -100). Reading identical positions with averaged sampling, I get (197, 161, 145) on 08 and (183, 146, 131) on 05. (The measurement is not as straight-forward in this case, as I had to manually align 05 and 08, as DT crashed during the process and I failed to position the preview window at the exact same pixels). Thanks in advance, Kofa ------------------------------------------------------------------------------ Dive into the World of Parallel Programming! The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net _______________________________________________ darktable-devel mailing list darktable-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/darktable-devel
