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Re: CMY vs. K only Neutrality

on 30/05/2002 22:24, Scott Griswold at email@hidden wrote:

> however, the areas that contain large amounts of K separate and
> appear to be too Magenta. If I continue to pull Magenta out of the profile
> then the CMY areas start to look too green.
As you find, there has to be a choice between a near perfect grey bias , or
a near perfect saturated color balance. Profile M Editor has a grey balance
correction but on my machine it breaks up the integrity of the highlight
pure colors. In theory it's as easy as modifying this grey component (if you
like rather the narrow side of near a+b values). This would still alter your
printer's grey after the linearisation , therefore invalidating the baselin
that you made and profile.

> What determines how K separates into neutral CMY? Is there a component
> within a profile which handles this part of the separation?
The centre of the composite is looking for smaller moves than the twists and
curves around the saturated colors will have to do depending on the
linearity of the printer. When the curves have a lot of pulling to do in the
stronger colors there will be variances in the grey introduced. The number
of grid points can make more reference points, assuring finer variations but
still has to work in unison with the overall color corrections.

> how K separates apart from how the CMY values are rendered. Since K needs to
> become CMYK, this creates an interesting dilemma for keeping things neutral.
> Has anyone else found a need for this?
> I am editing with Profile Maker 4.0.

Yes Scott , this is need for every CMYK rip, yet not well addressed. The
best solution is to use a early black start and maximum width to raise and
replace the composite grey with ink tank black. Not always pretty with
pastels and skin tones but the grey will be definitely more stable with
little or no color shift. There will be people who will then say that the
black then is not the right color. They'll be correct. Catch 22. Back to
composite grey and the problems from before.
There will be a slight advantage (or big depending on printer/media) with
spectral data used for conversions. That's the future of where the inkjet
rip market will try. Anyone's experiences with this would be appreciated.

Neil Snape email@hidden http://mapage.noos.fr/nsnape
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References: 
 >CMY vs. K only Neutrality (From: Scott Griswold <email@hidden>)



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