Re: LAB values
Re: LAB values
- Subject: Re: LAB values
- From: "Peter Baumbach" <email@hidden>
- Date: Sat, 2 Aug 2003 12:03:49 +0200
Many thanks to Bruce and Chris,
Fri, 1 Aug 2003 23:39:23 -0600 Chris Murphy wrote:
>
The info palette's LAB values for RGB and CMYK documents by default is
>
based on relative colorimetric. Go into Color Settings, click the Advanced
>
checkbox, and change the Intent to Absolute Colorimetric. Make sure you
>
change it back before doing any mode changes (other than with Convert to
>
Profile), or try to trust Print With Preview's preview box.
Oh, I indeed forgot about the rendering intent setting in Photoshop (RWCM p.
335). Now the LAB values are the same.
On Fri, 8/1/2003 16:18:55 -0700 Bruce wrote:
>
Because the capture profile isn't perfect (or you made a booboo in
>
the handbuilding). The differences shown in the comparison between
>
predicted and actual LAB values on p 230 are better than most, and
>
are the product of doing many such comparisons to find the "ideal"
>
scanner gamma (which in this particular case, on my Flextight 848,
>
was gamma=3.0). An average delta-e of around 1.3-1.8 is fairly
>
typical. If the average is a whole lot worse than that, let me know.
I understand that the capture profile can almost never be perfect. I have
got an average delta-e of 1.22, on my Howtek 4500, gamma=2.5, Silverfast
software with calibration. The best 90% average delta-e is 0.64, the maximum
deviation is 15.56. That value seems a bit large. Any idea ?
Thanks,
Peter
peter baumbach - fine art photography
http://www.pb-photo.net
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