Digital BW, The Print

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, bruce greene 
<bagreene@v...> wrote:
> 
> 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@h...>
> > 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>

I'd first like to say that the best thing to do is try things out and see.

But here is my reasoning.   The QTR curves/profiles aren't based on the
photoshop gray space at all.  When you print and select "Same As Source"
you are just passing the data through without modification.  QTR gets
the raw data.  When you did all the linearization it was based on raw
pixel data -- it was not at all dependent on the gray space.  So the
existing QTR profiles should work just fine as long as the pixel values
don't change, hence Assign-Profile.   Another way to look at it is: do
I want to preserve the way the screen looks (use Convert) or the way the
print looks (use Assign).

So, we are we doing all this??

In the past, (without using softproof) the display and the print never looked
the same.  My idea with the new gray space is to bring those two different
looks closer together -- naturally at least one of them has to change.
It's kind of like a "for free, builtin, generic" softproof.  

> >
> > 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?

I don't know what really goes on inside, but that sounds plausible.  But I
don't think we "need" absolute in the QTR printing process.

Roy

> 
> -bruce
> >
> > Roy