Re: jump
Re: jump
- Subject: Re: jump
- From: "Roy Harrington" <email@hidden>
- Date: Fri, 23 Nov 2007 18:20:26 -0800
On Dec 22, 2007 3:46 PM, eugene appert <email@hidden> wrote:
> Klaus,
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> Thanks for your answer.
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> There is something I don't understand about "applies your working grayscale space".
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> I would have thought that the file data and not the L* would be affected by the target working space. Such that though L*50 is represented in a 1.8 space as 61% and as 54% in a 2.2 space, the L* value remains the same.
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> Unless you mean the info pallet applies the algorithm normally employed by Photoshop for mode conversions (.3 R + .59G + .11 B). But then why would the anticipated conversion values that the info palette displays change simply by extracting the a* and b* channels?
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> I am using the Gretag color chart as reference. If I convert the Lab file to grayscale via Photoshop menu mode conversion, I will always preserve the L* values, no matter what grayscale space is configured by default in my color settings. Equally the info pallet will display the exact L* values of the Gretag chart regardless of the grayscale space configured in my color settings. Yet if I deactivate the a* and b* channels the file brightens visibly on the screen, even though the info palette continues to display the original L* values. But if the lab file is now converted to grayscale or if the L* channel is dragged into another file ( even to another Lab file) , the info palette will now display the L* values as they appear on the screen, that is at least L*10 brighter.
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> Eugene
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> Eugene,
It is a curious behavior.
What's happening is that whenever you look at any multi-channel file
(LAB,RGB,CMYK)
and turn on just one of the channels it treats it as a "grayscale"
file. Notice if you
take an RGB file and look at just the R it displays as gray. To do
this it has to
treat it as some "profile" and not too surprisingly it uses your
grayscale working space.
It affectively "assigns" your grayspace to the single channel for
display purposes.
This can completely change the visible luminosity as seen on the screen.
In fact you can go into Color Settings and try different grayspaces
with Preview on.
When you convert to gray you'll be getting a "convert-to-profile"
whereas with the
single channel view you are seeing an "assign profile".
Roy
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| | >re:jump (From: "eugene appert" <email@hidden>) |