[argyllcms] Re: Printer RGB profile and dark tones problem

  • From: Florian Höch <lists+argyllcms@xxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Sun, 14 Nov 2010 19:15:00 +0100

Hi,

Am 14.11.2010 18:33, schrieb Vittorio Villani:
I am using this command to generate an ICM profile for my Epson 4880
printer.

colprof -v -qh -no -np -ni -i D50 -o 1931_2 -S AdobeRGB1998.icc -cmd
-dpp -kz printerprofilename

Just out of curiosity, what's the reason for the -no -np -ni (I do not have much experience with using those parameters)?

I started from a 1500+ target and I am using a ColorMunki.

I am happy with the result for colors but I have some problems in the
dark tones of the images that I print.

Using a print test like this:
http://www.northlight-images.co.uk/article_pages/black_and_white_test.html
In the 21 step wedge I can read only 19, the darkest ones are all the same.

The main gripe I have with this test picture is that it has a "Gray Gamma 2.2" profile embedded. Honoring this profile, it means the two darkest steps are only L=1 apart, while the distance of the other steps are between L=4 and L=7. So, it seems to me that it should be normal for the two darkest patches to be hard to discern, even more so if you take the surrounding paper white and the resulting flare when viewed into account.

The paper is a good paper (FineArtBaryta) and using Epson ABW I get no
problems.

Please notice that I had the same problem with the ColorMunki software
generated profile and with the Epson canned profile.

Any suggestion? How can I improve the darker area of the image? Do you
have similar problems?

The way I see it the problem is in the image itself, ie. its embedded Gamma 2.2 profile. One way to improve the differentiation of the dark tones could be to change the way the values are to be interpreted, by assigning a different profile (e.g. sGray, which puts the two darkest steps 4 L levels apart and also lights the other darker grays a bit, while keeping most of the remaining tonal characteristics).

Regards
--
Florian Höch


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