QTR-Quadtone RIP

On Friday, August 11, 2006, at 04:40  AM, milogiacomorambaldi47 wrote:

> --- In QuadtoneRIP@yahoogroups.com, "Roy Harrington" <roy@...> wrote:
>>
>> If you use the printing profiles the editing space is not critical.
>  I still use the gray-lab for my scanned negatives since there is no
> "inherent" space but GG2.2 is a perfectly good working space too.  If
> you shoot digitally and the camera produces AdobeRGB color files GG2.2
> is a good match.
>>
>> Qimage only handles RGB files internally so gray files are converted
> to RGB on input.  RGB versions of my ICC profiles are really still
> grayscale profiles with R=G=B so that Qimage can use them.   BTW,
> Adobe InDesign is another major product that does not handle grayscale
> -- just RGB and CMYK.
>
> To recap, running the highly tweaked GG2.2 test image (8-bit JPG)
> straight to QTR works great.  Running the GG2.2 image through Qimage
> (converting to QTR-RGB-Matte) to QTR blocks up the shadows.  Running
> the GG2.2 image through Qimage (with no ICC conversion) to QTR works
> great.
>
> So... trying to move toward editing with a standard working space of
> QTR-GrayLab and printing with QTR-RGB-Matte, I loaded the GG2.2 image
> into PS, *converted* (not assigned) it to QTR-GrayLab, and saved it.
> Running that through Qimage (converting to QTR-RGB-Matte) to QTR
> blocks up the shadows again!

When you have multiple conversions, it's only the last one that makes 
any difference.
So:
GG2.2  ->  QTR Matte Paper
and
GG2.2  ->  GrayLab -> QTR Matte Paper
will yield the same print results.  L* is maintained during the 
conversions.
(the last conversion is a little different because of 
BlackPointCompensation)

It sounds like in your system, you can "highly tweak" based on your 
display and
get matching prints with just GG2.2.    Matching prints is the goal so 
I'd stop there.
If at some time you custom calibrated your whole system, maybe you'd 
get even
better matching.

>
> What's happening?  Is it simply not possible accurately to convert
> from GG2.2 to QTR-GrayLab on a highly tweaked 8-bit image?

The conversion should be fine -- the display didn't change did it?

> The histogram certainly changed shape somewhat.  Might this have 
> worked if
> the GG2.2 image were 16-bit?

The visible differences would be very small.  16-bit is good for 
editing since
you don't build up errors.  But when you are all done, 8 bit is good 
enough as
long as the conversion is done well -- (Photoshop does a good job of 
it).

>
> If not, then I'm still confused.  Otherwise, then perhaps there's hope
> for my previous workflow, which begins with Canon RAW files, then
> Adobe Camera Raw, then 16-bit ProPhotoRGB, etc.  I'm hoping that
> converting to QTR-GrayLab early in the process, editing entirely in
> 16-bit, converting to 8-bit only when all is ready, then converting to
> QTR-RGB-Matte with Qimage, and finally printing with QTR... will do
> the trick.  Sound plausible?

Since you report good prints with GG2.2, just do the final conversion to
GG2.2.   It doesn't matter what profile you use in the interim, 
especially
since it sounds like you'll be in 16-bit mode.   You could go from Raw
directly to GG2.2 and stay there from then on.   BTW,  I'm not very 
familiar
with the ProPhotoRGB but I did look it up and it happens to be a gamma 
1.8
space.

Roy

>
> Michael
>
>
-
Roy Harrington
roy@...
Black & White Photo Gallery
http://www.harrington.com