Photoshop Lab values
Photoshop Lab values
- Subject: Photoshop Lab values
- From: "Fleisher, Ken" <email@hidden>
- Date: Mon, 09 Jul 2007 09:03:25 -0400
- Thread-topic: Photoshop Lab values
Hello. I have encountered a strange result that I don't understand.
1) Create an RGB document in Photoshop in ProPhoto RGB color space.
2) Fill some blocks with solid colors where R=G=0
and B = [0, 17, 34, 51, ..., 255]
3) Read Lab values with the color picker (single pixel)
When I do this I get the following result:
R G B L a b
0 0 0 0 0 0
0 0 17 0 0 -12
0 0 34 0 3 -32
0 0 51 0 6 -49
0 0 68 0 11 -63
0 0 85 0 17 -76
0 0 102 0 24 -88
0 0 119 0 31 -99
0 0 136 0 40 -110
0 0 153 0 48 -120
0 0 170 0 55 -128
0 0 187 0 63 -128
0 0 204 0 70 -128
0 0 221 0 76 -128
0 0 238 0 83 -128
0 0 255 0 89 -128
What confuses me is that L* has a value of zero for all color patches.
Shouldn't L* increase as B increases? It doesn't seem logical that an RGB of
0, 0, 255 would have an L* of zero.
What am I missing? Any thoughts?
--
Ken Fleisher
Photographer
Imaging & Visual Services
National Gallery of Art
Washington, D.C.
Phone: (202) 712-7471
email@hidden
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