30 years young! could you please try what tobias suggested? the slightly longer answer is that Lab is an interesting colour space, so is your camera rgb. the colour matrix produces mostly matching colours for usual tones, but due to the linear approximation this matrix represents, it pushes out colours that are considered less important (the blues in this case).
these out-of-gamut/imaginary stimuli result in negative L values in the pipeline. that's a non-issue if you just convert to Lab and back. as soon as you enable any module that makes reasonable assumptions about Lab (like, L >= 0), you'd clip the values to the gamut of Lab, resulting in the purple cast. hope that helps. j. On Thu, May 18, 2017 at 6:26 AM, I. Ivanov <[email protected]> wrote: > In 30 years - I have never seen a graphic program of any kind to behave in > such a way and it would be considered "normal". The only settings available > are brightens, contrast and saturation and they are not altered by any > number. There should not be any change to the image. > > Regards, > > B > > > On 2017-05-17 11:16 AM, [email protected] wrote: >> >> On Wed, 17 May 2017 11:11:43 -0700 >> "I. Ivanov" <[email protected]> wrote: >> >>> My expectation is that if I am to enable the module and do not >>> modify any of the values - brightness / contrast or saturation - all >>> of them remain zero - then it should not alter the image (but it >>> does). >> >> I think that it is not a "correct" expectation. >> >> 1. If it was, then all modules would be enabled all the time. >> 2. All modules have default values and/or effects. Enabling the >> modules should apply these values/effects. >> > > ____________________________________________________________________________ > darktable user mailing list > to unsubscribe send a mail to [email protected] > ____________________________________________________________________________ darktable user mailing list to unsubscribe send a mail to [email protected]
