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

  • From: Vittorio Villani <vittoriovillani@xxxxxxxxxxx>
  • To: ArgyllCMS List <argyllcms@xxxxxxxxxxxxx>
  • Date: Sun, 14 Nov 2010 19:39:24 +0100

Thanks for your answer Florian.
I can easly understand now why that patches look all dark: my profile starts 
from L* 4 as darkest point...
I will write a mail to Keith asking him about his print test imge.
The reason for the -no -ni -np parameters is that, according to an expert that 
I have asked for some suggestions using colprof, this gives better gradients. 
Withoud this 3 options he got steps in many gradients. So I just followed his 
If you have never tried with that parameters try them and let me know what do 
you think about it.

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


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