[argyllcms] Re: rgb printer calibration

  • From: Radek Doulik <radek.doulik@xxxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Sun, 23 May 2010 14:28:55 +0200

On Sun, 2010-05-23 at 11:25 +1000, Graeme Gill wrote:
> Radek Doulik wrote:
> > I am trying to create chart for RGB printer calibration. I run targen
> > with these options:
> > 
> > targen -v  -d2 -s52 -e3 -f0 linearization-target
> > 
> > The resulting chart contains RGB values of CMY color shades. I was
> > expecting to see color shades of red, green and blue. Is it a bug in
> > targen, or do I miss something?
> There is no red, green or blue colorant in your printer. It uses
> Cyan, Magenta and Yellow colorants, so there is no point attempting
> to linearise things that don't exist.
> [Notice that the common point of R/G/B test wedges is black, while the
>   common point of C/M/Y wedges is white. Given that in printing the
>   media color is white, it makes no sense to use R/G/B/ test wedges.]

Thanks for your answer. Looks like I should have had to read the
documentation better ;-), I missed it on first reading. I still wonder
though if it might help a bit in my case, to try linearize these virtual
RGB channels.

I have a CMY termosublimation printer, where the driver is 8bit RGB
driver, which allows to fine adjust "curves" of RGB channels, but not of
CMY. So my plan was to use results of printcal to adjust the virtual RGB
channels, before profiling the printer, so that I don't loose anything
from 256 levels.

I have already profiled the printer without calibration, but I see
problems in gradients close to white when using perceptual intent (for
example soft shadows on white background are not smooth). OK, if I
forget about calibrating the virtual RGB channels, do you think that
using result of printcal in printtarg might help with that, when only
8bit driver is available?


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