On a sidenote, when I sent my photos out to be printed a while ago I
actually did have an ICC file for their printers, and I failed to apply it
in darktable: I found the output color profile module, but it only lists
the default profiles and does not offer any way to select a custom ICC file.
After Tony's message I double checked and noticed the tooltip says to copy
the ICC files in a specific directory! That's good to know. An obvious
feature request would be another option in the dropdown "Custom ICC
profile..." (or something to that end) which pops up a file selector doing
the copying for you.
Cheers
Moritz
On Sun, Jun 16, 2013 at 8:45 PM, Tony Arnold
<[email protected]>wrote:
> Julian,
>
> On 16/06/13 18:18, Julian J. M. wrote:
> > I clearly don't master color management... I hope some of you can
> > enlighten me.
> >
> > I have an ICC profile for my monitor, created with a Pantone Huey Pro.
> > Actually I have one for each monitor, and darktable picks the correct
> > one depending on which monitor it's on.
> >
> > Main screen:
> > [color profile] we got a new screen profile from the _ICC_PROFILE (size:
> > 18660)
> > Secondary screen:
> > [color profile] colord gave us a new screen profile:
> > '/home/julian/.local/share/icc/GCM - Hewlett Packard - HP 2311x -
> > 3CQ21701N9 (2013-04-04) [15-31-56].icc' (size: 18648)
> >
> > So far so good. I know my monitors are kind of crappy ones, and that the
> > calibrator is not a spectrophotometer. Anyway, both monitors have a
> > diferent tint when no ICC profile is applied (gnome colord), and
> > darktable look the same on both when they are applied.
> >
> >
> > I've sent some pictures to print (3 different online shops), and they
> > resulted quite darker than what I see on screen. A lot of dark zones
> > detail is lost. All 3 with very similar results. Also, the exported jpgs
> > are darker that what I see on darktable, when I see them in the the
> > browser (Google Chrome). The profile I use when exporting is sRGB
> > perceptual.
>
> I think you need to calibrate your printer. Not sure if your calibration
> device has that capability, but if it does creating an ICC profile for
> your printer would be a good idea.
> >
> > Now, playing with the Output Color Profile module... I see that the
> > screen profile is set to "system profile". If I change it to sRGB, the
> > image I see (darkroom) looks exactly the same as the exported JPGs. I'm
> > not sure what I'm changing here... Is the monitor ICC profile ignored if
> > I change this?
>
> Once you have a printer profile, you either need to use that when
> exporting jpeg in DT and ensure that your system does not use the
> profile when printing. Or, set the system to use you printer's profile
> then set the exported image to use sRGB (I'm not sure on this step, to
> be honest).
>
> Here is what I think happens. After demosaicing, the RAW file is
> converted to an internal colour space using the camera's ICC profile.
> The internal colours are converted using the screen's profile. When you
> export an image, the profile in the image is used to convert the pixel
> values in the image back to this internal form and then the printer's
> profile is used to convert this internal form back to pixel values for
> the printer.
>
> Every device has a gamut, which represents the limits of the colours
> that device can accurately display. Screen gamuts are much larger than
> printers, so the outputs may look different if on the screen you see
> colours the printer cannot reproduce.
>
> Having everything calibrated and the right profiles used everywhere
> should minimise the differences.
>
> Regards,
> Tony.
> --
> Tony Arnold, Tel: +44 (0) 161 275 6093
> Head of IT Security, Fax: +44 (0) 705 344 3082
> University of Manchester, Mob: +44 (0) 773 330 0039
> Manchester M13 9PL. Email: [email protected]
>
>
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