David Purton schrieb:
On Thu, Feb 17, 2005 at 11:26:47AM -0600, Bob Friesenhahn wrote:
On Wed, 16 Feb 2005, David Purton wrote:
I would have thought that if my input profile and my proofing profile
are the same, then all colours are by definition in gamut.
Are you sure that the colors used in your images are within the gamut
of your input profile? Maybe they are out of range in the first
place.
How can C100 M100 Y0 K0 be out of gamut in a four colour process?
It's just a mix of inks on a page.
100% Cyan is not marked out of gamut by liblcms.
100% Magenta is not marked out of gamut by liblcms either.
You are going to *something* (a dark blue colour) when you print the two
plates together. That *something* is what is specified by C100 M100 Y0 K0.
So surely by definition that *something* is in gamut?
What do I miss?
No, you don't miss anything. You just make the assumption that the gamut
warning is perfectly accurate. However, it isn't. Its accuracy is
limited. According to the A2B1 and gamut LUT in the ISOcoated.icc
profile, the gamut boundary in this sector of the color space is
approximately at CMYK=[96,96,0,0]. Yes, this is slightly inaccurate,
since I agree it should be at CMYK=[100,100,0,0] (as you expect), but
it's IMO still an acceptable difference. Maybe you find other profiles
which are more accurate, but at least this profile isn't.
Regards,
Gerhard
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