[argyllcms] Re: Manual channel limits doesn't work in printcal for RGB-printer

  • From: Nikolay Pokhilchenko <nikolay_po@xxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Sat, 12 Dec 2009 16:49:52 +0300

Nikolay Pokhilchenko wrote:

> V1.1.0_RC1, Windows Vista:
> When calibrating an RGB-printer, it's impossible to achieve the "darkest" 
> black R=B=G=0 in the calibration result if the printcal have select the other 
> limits. Even if I use "-x r 100", "-x g 100" and "-x b 100" keys.
> Try my printer example attached.
> The workflow:
> targen -v -d2 -f0 -m0 -e9 -s274 Lin
> printtarg -v -ii1 -A0.6 -a0.8 -m0 -L -T360 -p240x225 Lin
> chartread -v -a Lin
> printcal -v -p -i -x r 100 -x g 100 -x b 100 Lin
> If You try "printcal -v -p -i Lin", the curves will be the same.
> If I print the next targets by printtarg with -K"Lin.cal" function, the 
> R=G=B=0 output TIFF level isn't achievable. So there is heavy gamut 
> restriction from the black side.

In RC2 The problem is still here. Even with 100% user channel limits in 
printcal, the printtarg result didn't translate R=B=G=0 to zeros. For example, 
the RGB=0,0,0 after printtarg with calibration become 0,21,0. It's heavy 
restriction for RGB-printer gamut. So printcal for RGB printer is useless.
The problem is in printcal itself.
The example device profile (one A2B only) is attached.

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