Re: Photoshop Lab values
Re: Photoshop Lab values
- Subject: Re: Photoshop Lab values
- From: Graeme Gill <email@hidden>
- Date: Mon, 09 Jul 2007 23:39:55 +1000
Fleisher, Ken wrote:
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)
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?
ProPhoto has an extreme Blue colorant value. The blue colorant in fact
has an almost zero Y value, hence pure blues have an almost zero
L* value. In this respect, since ProPhoto has a non-real world
blue colorant value, the colorspace itself shouldn't be treated
as a real world space anymore than XYZ or L*a*b* are.
[The blue colorant has a D50 L*a*b* value of about 0.08 90.25 -172.3].
Graeme Gill.
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