On Thu, Jan 29, 2009 at 00:04, Alastair M. Robinson wrote:Here's a raw plot of a CMYK stepwedge testchart - plotting input against L*, a and b. Note that there's already a pretty hefty (modified) gamma correction going on just to bring the stepwedge testpoints to something approaching even spacing - maybe this is hiding effects that might otherwise be visible? http://www.blackfiveimaging.co.uk/linearize/EpsonPQI_raw.jpg
Martin Weberg wrote:
I prefer plotting a and b together looking through the L plane, whichI think better illustrates how CMY would effect the final gamut.
Me too. The example plot <http://digitalproof.info/argyll/inklimits-ab.pdf> suggests that cyan can't contribute much to the gamut when it's driven beyond the bend. But where is the optimal point to clip it?
As Martin wrote, one of the problems whit ink limiting is that these decisions are often subjective and therefore not reproducible.
Another issue one should keep in mind are the secondary colors. I had to deal with printers/substrates where e.g. both cyan an yellow were perfect, but the resulting green rolled off the paper.
Klaus
