[argyllcms] Re: Black turning down problem - help!

  • From: Elena [service address] <1007140@xxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Thu, 06 Jan 2011 20:17:44 +0100

perhaps I'm solving the enigma!

After careful investigation, I discovered that on this paper and with these
inks (MISPro K4, only Photo K and Light K used to simulate littler dots)
the CMY combination (100 100 100 0) is actually DARKER than CMYK (100 100 100 
Adding black to the mix lightens up things! Oh well, one never stops learning...

Since I never usually ran over 300% ink for some practical reason, I just never
realized that! I knew well that 100,100,100,0 is always much darker than K with 
inks, and pretty on every paper I use (glossy also) - but I never imagined that
CMYK could be lighter than CMY, really.

So I finally see some sense to the black ramping down behavior. It must
ramp down, because adding C,M,Y to 100% K would result in a lighter mix, and
the only solution colprof sees is diminishing the black.

Well. I'm not fully convinved yet on this being the better choice, however,
since I think an experienced user (and argyll is for them, isn't it ?)
usually knows what he does when he choses things such as ink limits and
black generation parameters. So he expects to have the full responsibility
on what happens.

I never understood well the actual aim of the -K parameter
("Same as -k, but target is K locus rather than K value itself")
but I suspect that the relative behaviors of -k and -K are swapped...
it perhaps should be

 -k = obey blindly the user choice
 -K = follow the user choice as a guide line, but give priority to
      what actually are the measured lightest and darkest device values


Other related posts: