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 13:30:49 -0800
At 11:43 AM -0800 2/23/02, Bruce Fraser wrote:
At 10:35 PM -0800 2/22/02, Mark Burgess wrote:
At 5:55 PM -0800 2/22/02, Thomas Knoll wrote:
Seems to me that in the cmyk -> k translation, the k values should
be used as a sort of threshold -- colors + k can cause it to go
darker, but k alone should not be lightened.
That's what happens. It's not lightening 100K, it's producing the
literal luminance of 100K.
You can say that it's not lightening it, but it really is -- print
the two images and one will be lighter. There are two *different*
literal luminances of 100k, one of which is in fact lighter than the
other. It's not necessary to have any kind of measuring device to see
this -- solid black changes to screened black.
(If 100K translated to black, it wouldn't leave any room for
colors+k to go darker.)
That's exactly what I'm looking to do -- let 100%k be the top
threshold and let everything darker than that go to pure black. If I
have a nice magazine ad with rich blacks in the photo and good solid
blacks in the type and logo, I am not going to want (or expect) that,
in grayscale, the two blacks would be distinguishable from one
another.
Obviously grayscale has a smaller tonal range than cmyk. When
Photoshop converts cmyk to grayscale it compresses the cmyk tonal
range to fit that of grayscale. Although that allows a certain amount
of shadow detail to be retained, it has the unfortunate effect of
distorting the values for straight black. I imagine that it also
necessarily causes banding in the lighter areas due to fewer values
being available to represent those tones. I would have do to some
testing to see
--
Mark
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