[Openicc] ALL YOU NEED IS A PROFILE, THE MYTH. (WAS CC Profiles In X Specification and dispwin)

[Graeme Gill]

Robert Krawitz wrote:

> I'm not so certain about this.  The purpose of using light inks is to
> reduce the grain; I don't believe that it actually increases gamut.

If you explore the full gamut of some printers, they can in fact
increase the gamut. Even on their own they can increase the gamut -
a hand waving explanation is as follows:

To produce a light tint using dark ink require half toning. The half
toning places dots of the saturated color ink interspersed with the
white (highly un-saturated) media. The media color desaturates the
the ink color. A purpose created light ink might achieve the same
reflectance level with 100% coverage, thereby not allowing the
media color to desaturate the result, thereby achieving increased
saturation at light tints.

Some experiments I performed on a CMYKcmOG printer indicated that
some combinations of the cm and OG inks produces some very
interesting light, highly saturated colors. Actually exploiting
such behavior may not be easy though.

> A while back I did some thinking about how to adjust the light/dark
> ink tradeoff depending upon the total ink load, but I never got very
> far...

I suspect such an approach may be too intricate to implement, and
hard coding such an algorithm into the print pipeline makes it
rather inflexible.
The ink limiting in a profile can account for the ink load
introduced into a composite channel or due to a separation step.
You just need a format to feed this information into the profile
creation.

Graeme Gill.