Digital BW, The Print

On Wednesday, Dec 8, 2004, at 15:13 US/Pacific, 
DigitalBlackandWhiteThePrint@yahoogroups.com wrote:

> Message: 13
>    Date: Wed, 08 Dec 2004 21:12:25 -0000
>    From: "Roy Harrington" <roy@...>
> Subject: Re: LAB Step Wedge -- a grayscape Lab space
>
>
>>
>
> The new space does several different things.   For printing through QTR
> there is no effect.  Remember in the Print with Preview we select Same
> as Source for the print.   We still have a grayscale image so this 
> means
> the exact pixel values are sent to QTR.
> For display though -- what you see on the screen -- there's still a 
> bunch
> of color management going on.  The pixels go from the gray space (now
> just L) to Lab to the RGB of the monitor.  Before they went from gamma 
> 2.2
> to Lab to RGB.   So the new way we see the difference between 95 and 
> 100
> on the screen as well as on the print.
>
> The bottom line is that you should Assign to the new space NOT Convert 
> to it.

Are you sure Roy? Sure the data stays the same, but our view of it 
changes (especially in the darkest tones) and we edit the image 
differently to compensate for the new LAB working space.

What I don't understand, is that if I have a QTR curve that works for 
gamma 2.2 space, then I would need to create a new curve for a LAB 
working space. If I create such a new QTR curve that works for LAB 
space and not gamma 2.2 then I would want to "convert to profile" when 
changing from gamma 2.2 image to a LAB greyspace image.

If I don't create a new QTR curve, then I loose my visual screen to 
print match, even if I can make the the original print while working 
from LAB space. It's hard to write this stuff and have it make sense! 
But it makes perfect sense to me <g>
>
> You are right that absolute values will vary based on dMin, dMax, the 
> kind
> of display you use, the lighting etc...  I lean toward the everything 
> relative
> point of view though.   With color management there are the different
> renderings and Perceptual is usually the one of choice.   This 
> corresponds to
> the compressing the gamut mode.  The Absolute Colormetric is more like
> your view but seems rarely used.

Absolute colormetric  is used when proofing a low gamut output on a 
high gamut output device. (like what would newsprint look like printed 
on my epson 1280?) Isn't it also used in softproof profiles or 
conversions?

-bruce
>
> Roy