[cairo] Subtractive API, part 0

Chris Murphy lists at colorremedies.com
Mon Feb 1 08:00:23 PST 2010

On Jan 30, 2010, at 1:44 PM, ecir hana wrote:
> But I have my guesses. First, I think it is useful to split your
> question into two: additive and subtractive spaces. If you produce a
> milion of cameras with the same lens I would guess it is somehow
> possible to calibrate them. I also read, that some people are able to
> see that one lens has slightly different color cast that the other
> one. Anyway, I would guess that in the former space you have fairly
> good amount of control over the whole devices. Contrary to printers.
> The final result is formed by many pieces, like paper, coating, diyes,
> opacity, drying rate, printing speed, ... These many aspects are
> combined to just one color, which is why it is so difficult to get it
> under control. I would call the current situation far for "nearly
> completely" solved.

All of these things have been completely solved, short of actually simulating metallic and fluorescent spot colors with conventional inkjet inks. You can simulate the effect of ink opacity and print sequence. This is done automatically, millions of times a day, all over the world, with CMYK ICC profiles which take all of these things into account. Extending this to spot colors can be done either using deviceN ICC profiles, or proprietary solutions which tend to be more common.

> Also, I think it is very important to notice that while on a monitor
> you are able to display and measure a color and to tweek the ICC
> several times, in print you usually get only one shot because to print
> twice is two time more expensive.

Next to no one is tweaking ICC profiles anymore. And if it's done, it's done during the ICC profile testing phase, prior to putting a profile into production use. Once in production use, it is not modified any further, rather process control is used on press to maintain press behavior so it conforms to the established printing condition.

Chris Murphy
Color Remedies (TM)
New York, NY
Co-author "Real World Color Management, 2nd Ed"

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