On 02/02/2013 10:14 PM, Richard Levitte wrote: > Hi, > > for a moment, I thought I had found a HUGE bug in darktable. You see, > I had just calibrated my screen (wow, grey really looks grey now!), > and was surprised to see that darktable suddenly gave me very > different results in development mode. The histogram looked awfully > wrong, the left end of the green channel would for example never move > left, it stopped a bit in from the left of the histogram, and colors > were all weird. > > It took me a moment to notice the display profile choice in the output > color profile module. Changing it to something like sRGB made things > quite a bit better. > > Something I noticed was that the change of display profile changed the > image histogram... and that has me surprised. Why should the display > profile affect the image histogram? I can understand if output and > softproof profiles affect the histogram... but *display*? > Truly, this looks like a bug to me... however, not as huge as I first > thought, but still a usability bug. It makes me distrust the > histogram. > > Cheers, > Richard > Hello,
I will try to exlplain why this is not a bug, my comments are valid until our colormanagement guru says otherwise.... First of all, please read and follow: http://blog.pcode.nl/2012/01/29/color-management-on-linux/ Make sure your display profile is correctly installed and loaded, and _ICC_PROFILE is correctly set (correctly means it is set at all). If this happens your screen should change slightly. Now darktable is able to load and use your profile. It is not necessary to set the display profile it in the profile iop, as it is on "system default". Regarding the histogram, it is correct that it changes with your display profile. You are working in a defined colorspace if you profiled your monitor and calibrated it correctly. What you see is the representation of this colorspace. The advantage of working with darktable and RAW files is that they have _no_ colorspace to begin with. So everything you do you do in the working colorspace of your monitor, which is the greatest colorspace you can _see_. The histogram is a representation of this. A histogram is not absolute for a picture without a color profile. You could "fix" the histogram by setting everything to "adobe sRGB", for example, but this would limit your working colorspace. The colorspace of the picture is only relevant for export, there you decide which colorspace the image should have (e.g. sRGB) and darktable converts the data from the working colorspace to the output profile. If you have a wide gamut monitor and you export to sRGB, you will see that the output is not what you saw in darktable if you image viewer is color managed (geeqie, eog i believe), because you are looking at a picture with a smaller (or different) colorspace than your monitor can display. Hope this helps, hal ------------------------------------------------------------------------------ Everyone hates slow websites. So do we. Make your web apps faster with AppDynamics Download AppDynamics Lite for free today: http://p.sf.net/sfu/appdyn_d2d_jan _______________________________________________ Darktable-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/darktable-users
