[Darktable-users] How to fix out-of-gamut areas

[Robert William Hutton]

Hi All,

I've recently been preparing some photos for printing, so I've been trying to work out the whole colour managed workflow
thing. I think I've finally got my screen properly calibrated with my ColorHug, and have loaded the print profiles from
the printing company as output colour profiles in darktable. When I go to check the gamut of my photos, I find that
they're often way outside the printable gamut:

Loading Image...

Does anyone have any strategies they could recommend to manually bring these images back inside the printable gamut? Or
would I be better off exporting the images with the printer profile selected and with the intent set to perceptual? My
problem with that is that the exported images sometimes look really weird in geeqie:

Loading Image...

And even worse in the GNOME Image Viewer:

Loading Image...

I see really saturated colours that look like they're clipping and serious loss of highlight detail. However, the image
looks much better in GIMP (this is without converting the colour profile to sRGB):

Loading Image...

All of these programs are ostensibly colour managed. I guess I'm also wondering whether this is a valid approach to
soft-proof the images before sending them? Should I just go ahead and send a few of these to the printer and see how
they turn out?

Thanks for any advice,

Rob

[Markus Jung]

Post by Robert William Hutton
Does anyone have any strategies they could recommend to manually bring these images back inside the printable gamut?

Disclaimer: Just some half knowledge
Softproof shows you how the print result (most likely) will look like.
If you do not like the result of the automagic gamut mapping, you
can/should develop your RAW to fit into the printer gamut -> until all
areas which are important to you do not show gamut warnings any more.

Post by Robert William Hutton
Or would I be better off exporting the images with the printer profile selected and with the intent set to perceptual?

No. Thats plainly wrong. You export to some standard color space like
sRGB, AdobeRGB or ProPhotoRGB. If the image is processed for printing,
the colors are converted from this color space to the printer color space.
Display color management works the same way.
Standard color space -> Device color space.
How did you export them/to which color space? The result looks pretty
strange. Regarding color management, i would most likely trust GIMP and
Geeqie first, and eog not that much ;)

Post by Robert William Hutton
I see really saturated colours that look like they're clipping and serious loss of highlight detail. However, the image

Without converting what? Can you explain this a bit more?

Regards,
Markus

[Elle Stone]

Post by Robert William Hutton
I see really saturated colours that look like they're clipping and serious loss of highlight detail. However, the image

Those saturated highlight colours look like they really are clipped (out
of gamut). Printer (and also working space) color gamuts get smaller as
you approach white. Try lowering the saturation in the highlights and
perhaps making the highlights not quite so bright.

Elle

[Rob Z. Smith]

Markus said
" Softproof shows you how the print result (most likely) will look like.
If you do not like the result of the automagic gamut mapping, you can/should develop your RAW to fit into the printer gamut -> until all areas which are important to you do not show gamut warnings any more.

Post by Robert William Hutton
Or would I be better off exporting the images with the printer profile selected and with the intent set to perceptual?

No. Thats plainly wrong. You export to some standard color space like sRGB, AdobeRGB or ProPhotoRGB. If the image is processed for printing, the colors are converted from this color space to the printer color space."


I think all of the above is good advice and sending your printers an sRGB image is going to be the safest option but it does depend on what your printer will accept. For example the printers I use will accept either an image in sRGB or one explicitly exported to their printers colourspace but not AdobeRGB or anything else.

So I would say always use SRGB, unless there are areas out of gamut in SRGB *and* in gamut for your final print device *and* you are really interested in those out of gamut areas and not prepared to tweak them to be suitable for SRGB. If you really,really,really want to do this you then need to send the image to your printer in some wider gamut colourspace and that choice of colourspace to use is going to be determined by what your printer is prepared to accept. Even then I would assume that, until proved otherwise, the printers are highly likely to cock up non-routine colourspaces and so make life easier for them (and you) by just sending SRGB :-)

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[Stéphane Gourichon]

Post by Robert William Hutton
Hi All,
I've recently been preparing some photos for printing, so I've been trying to work out the whole colour managed workflow
thing. I think I've finally got my screen properly calibrated with my ColorHug, and have loaded the print profiles from
the printing company as output colour profiles in darktable. When I go to check the gamut of my photos, I find that
https://www.dropbox.com/s/1v4ulmsw8rvnffk/Vignette%20on%20top%20of%20out%20of%20gamut.png

Hello,

I don't know at all from what background/in what situation you are and
for the sake of efficiency take some shortcut. Please pardon me and
correct me if I'm wrong or misguided.

Is the intense saturation something voluntarily added ? I can't believe
it was in the real scene.

Also, if your pictures are so wildly out of gamut in darktable *and* so
saturated in external programs, something must be wrong.


When opening a RAW, darktable by default applies a base curve which
happens to increase saturation a lot, just like most cameras do when
shooting JPEG.

For this reason, for most usages now I shoot RAW and turn off base curve
in darktable to start from something closer to reality. The first time
I did so, I was shocked by the apparent loss of contrast. After that I
learned how it is actually a much better starting place, giving much
more details and easier control.

When the subject appears to lack saturation (which is probably not the
case here), instead of enabling base curve or fiddling with curves I
first try to just enable velvia effect.

Does this relate to your experience ?

Regards,