In message <canqv4twj9bt4zuqwjjyqka42bhtmcjazysgvrjtct5ba01v...@mail.gmail.com> on Mon, 4 Feb 2013 22:04:21 +0100, Pascal de Bruijn <[email protected]> said:
pmjdebruijn> On Mon, Feb 4, 2013 at 9:46 PM, Richard Levitte <[email protected]> wrote: pmjdebruijn> > In message <CANqV4tVGpe0zqg4K1=shvvztah1z7sq4qhsoe7x1q6f3iqm...@mail.gmail.com> on Mon, 4 Feb 2013 19:19:45 +0100, Pascal de Bruijn <[email protected]> said: pmjdebruijn> > pmjdebruijn> > pmjdebruijn> Double correction cannot happen (well unless you have a really highend pmjdebruijn> > pmjdebruijn> LaCie/EIZO display which can do hardware correction or something). pmjdebruijn> > pmjdebruijn> > Ok, in that case I'd like an explanation to what's happening to me. pmjdebruijn> > This all started with me color characterising my monitor (laptop LCD) pmjdebruijn> > and creating a profile for it (using dispcalGUI), then loading it pmjdebruijn> > (using 'dispwin -L'). Display colors became much better (grey is pmjdebruijn> > actually grey, not something with a blue tint). pmjdebruijn> > pmjdebruijn> > Then I started doing some work on some images I had taken just pmjdebruijn> > recently, and what I got was absolutely h-o-r-r-i-b-l-e. Basically, pmjdebruijn> > the three channels were kind of shifted in the histogram, and what was pmjdebruijn> > supposed to be a black background was now redish brown or some such. pmjdebruijn> > (I wonder if I could possibly produce a test, say by putting together pmjdebruijn> > a white .png, import it and see how it ends up). pmjdebruijn> > Changing my display profile from "system display" to "sRGB" gave me a pmjdebruijn> > better look. pmjdebruijn> pmjdebruijn> Sounds like an invalid profile? pmjdebruijn> pmjdebruijn> Did you use GNOME Color Manager to generate it? Nope, I used dispcalGUI (a ArgyllCMS tool, and as I understand it, GNOME Color Manager uses ArgyllCMS under the hood as well). [note: I wrote this above, as well as how I load the profile] pmjdebruijn> Which type of colorimeter did you use? ColorHug. pmjdebruijn> Do keep in mind that low end devices tend to be prone to pmjdebruijn> get invalid reading on some display types, particular pmjdebruijn> with newer LED displays. Mine is a standard backlit LCD display. [note: I wrote this above] pmjdebruijn> > pmjdebruijn> I have further details on anatomy of display profiles here: pmjdebruijn> > pmjdebruijn> pmjdebruijn> > pmjdebruijn> http://blog.pcode.nl/2012/01/29/color-management-on-linux/ pmjdebruijn> > pmjdebruijn> pmjdebruijn> > pmjdebruijn> If you still have any questions left, feel free to give me a bump. pmjdebruijn> > pmjdebruijn> > Yup, I've read it and it makes a lot of sense. What doesn't make pmjdebruijn> > sense to me is why there's a need for a program like Gimp and pmjdebruijn> > darktable to use the display profile to correct colors that are pmjdebruijn> > corrected through the VLUT (by the X11 driver, I assume)... pmjdebruijn> pmjdebruijn> It's not the same thing. Think of cooking, if you make something that pmjdebruijn> needs to be more salty and sweet, only adding the salt won't do the pmjdebruijn> trick. You need to add salt _and_ sugar. (sorry for the horrible pmjdebruijn> analogy :) Right, and that analogy doesn't explain anything to me, really. pmjdebruijn> The VCGT corrects for whitepoint and gamma. pmjdebruijn> pmjdebruijn> The matrix characterizes the displays gamut (which possibly means pmjdebruijn> shifting hue's and scaling saturation). And mapping input gamuts to pmjdebruijn> display gamuts can be a dynamic process when using the (for example) pmjdebruijn> commonly used perceptual rendering intent. And the VLUT is inherently pmjdebruijn> static. Right. I've assume that the characterisation I've done, and loading the profile I created is designed to make sure sRGB is rendered as correctly as possible, is that assumption close to correct? Furthermore, I assume that the display profile should make sure I see what I will get when exporting the picture. Is that close to correct? -- Richard Levitte [email protected] http://richard.levitte.org/ "Life is a tremendous celebration - and I'm invited!" -- from a friend's blog, translated from Swedish ------------------------------------------------------------------------------ Free Next-Gen Firewall Hardware Offer Buy your Sophos next-gen firewall before the end March 2013 and get the hardware for free! Learn more. http://p.sf.net/sfu/sophos-d2d-feb _______________________________________________ Darktable-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/darktable-users
