Re: Keep cmy out of matched grey
Re: Keep cmy out of matched grey
- Subject: Re: Keep cmy out of matched grey
- From: Chris Murphy <email@hidden>
- Date: Thu, 20 Mar 2008 21:02:25 -0400
You'll want to map L* = 100 to paper white, so that you do not get
"scum dots" on press. i.e. areas that are supposed to be white in the
original file, don't image on press.
Conversely for black, you kinda have a dilemma. The image will
contain, effectively L* values ranging from 0 to 100. A press cannot
reproduce L* = 0. Or 1, or 2 or 3...
On a decent #3 sheet (medium quality, used for higher quality
magazines and lower quality commercial printing), your 100% K only
goes to L* 15. You can't get anything darker than this.
For newsprint, it's maybe L* 18 or 20. (On top of that, it's likely to
be very non-neutral.)
Your image will contain important shadow detail that "lives" below L*
20. Yet all of it is going to be converted to 100% K if you go with
just a simple lookup. Black Point Compensation is going to dynamically
compress this so that L* =0 in the image is remapped to L*=18 (and
hence 100%). As L* increases, 100%K descreases in some uniform way as
to attempt to render some shadow detail whereas if you don't, it will
get clobbered.
Chris Murphy
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