Re: Photoshop 6 changing black to gray
Re: Photoshop 6 changing black to gray
- Subject: Re: Photoshop 6 changing black to gray
- From: Mark Burgess <email@hidden>
- Date: Sat, 23 Feb 2002 13:08:52 -0800
What you're missing is that, in CMYK, 100K isn't black.
Uh, yeah... I'd have ask around the studio to be sure, but I have a
feeling that the designers would disagree. :-)
But in any case that's missing the point. If I convert a cmyk image
to grayscale and print it alongside the original, 100%k should still
be 100%k. A solid black logo should still be a solid black logo.
In a theoretical and color-science sort of way I can see what's
happening. But as someone who needs to get paid for converting images
correctly, I have to maintain those values. If I have screens where
there were solids before I eat film. I can argue all day that PS6 is
technically doing the "right" thing but I will still not get paid.
The mistake that Photoshop is making is that it is changing the way
it defines black when it does the conversion. In the CMKY image,
100%k is defined to have a luminance of 12. Fine -- if I pull out my
spectrophotometer and measure the solid black patch, it says "12."
But when PS6 converts that to grayscale it redefines the luminance so
that now "12" means 78% black. This is wrong, because the ink color
has not changed. If I want the spectrophotometer to still read "12"
on the printed piece I have to have 100% solid black. I need to
either ditch the new scheme completely, or find a setting that says
something like "Use CMYK black for Grayscale images." This setting
would maintain the luminance so that in grayscale images the 100%K
would still report the correct luminance of 12.
One workaround is to define 100K as a spot color...
Hm, yeah, we did figure that out by trial and error for Illustrator
EPS files -- regular Illustrator black is defined as 100%k and does
not rasterize properly in PS6. If we changed that to be defined as a
grayscale black it was fine. But that is not practical for all of our
old stuff, or stuff that is customer-supplied, or pages that are
saved out of Quark, etc. It's much easier to just switch to PS4
emulation and forget about it. I really can't take the chance that
people will do the conversions using one of the PS6 settings.
--
Mark
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