Imprecise Lab values in Photoshop CS2
Imprecise Lab values in Photoshop CS2
- Subject: Imprecise Lab values in Photoshop CS2
- From: Marco Ugolini <email@hidden>
- Date: Fri, 04 Nov 2005 11:41:10 -0800
I vaguely remember a thread from a while back in this list in which people
discussed an anomaly in Photoshop CS2. I don't remember whether or not a
conclusion was reached.
The anomaly consists of the fact that, if you open a document in L*a*b*
color mode, enter certain L*a*b* values in the Color Picker, and then fill a
selected area of the image with the color you just defined, when you go back
to sample the color that you just filled the selected area with (with the
eyedropper in Point Sample mode to avoid spurious readings), often enough
you find that what you read is *not exactly* what you told the application
to put in.
Stranger still, if you do the *very same* procedure in *Photoshop CS* using
the *very same* values that were "misbehaving" in CS2, this time the values
in the image are exactly right on target. No changes.
If anybody wants to test for themselves what I just described, here is a
chart of sample values: in the first column are the Lab values as entered in
the Color Picker, in the second column the values that appear in an image
file in CS2, in the third column the values in CS:
---------------- ---------------- ----------------
Color Picker Photoshop CS2 Photoshop CS
---------------- ---------------- ----------------
L* a* b* L* a* b* L* a* b*
---------------- ---------------- ----------------
87 2 114 87 1 113 87 2 114
44 78 8 44 77 7 44 78 8
80 -25 88 80 -25 87 80 -25 88
19 40 -79 19 39 -79 19 40 -79
60 -78 2 60 -78 1 60 -78 2
25 6 12 25 5 11 25 6 12
My question is:
- Is this a bug in Photoshop CS2?
- Is there a way to fix it?
- If it's a bug, is Adobe aware of it, and are *they* going to fix it?
Thank you.
--------------
Marco Ugolini
Mill Valley, CA
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