QTR-Quadtone RIP

Ernst,

Thanks for your reply. I think there may be some confusion about the 
use of the term grayscale. For instance, when I use the Channel Mixer 
and check the Monochrome box, I get a monochrome RGB image (three 
channels, R, G and B and all pixels have the same R, G and B values), 
not a grayscale, single channel image. As long as I keep my image in 
the RGB mode, the Gray settings in Photoshop Color Settings don't 
come into play. When you say that any other tone corrections should 
be done in grayscale afterwards implies that you change the mode from 
RGB to Gray and my point is that you don't have to do that at all and 
stay in RGB mode "till the bitter end".

I don't want to nitpick or repeat what I have said in other posts, 
but your recommendation to select either Gray Gamma 1.8 or Gray Gamma 
2.2 for the Gray Working Space is inconsistent with Roy's to use QTR -
 Gray Lab (if you don't want to use the RGB mode). And that's an 
issue that I see a lot on this forum: recommendations that are 
inconsistent and/or contradictory. I rest my case for an overhaul of 
the documentation.

Best regards en de groetjes,

Frans Waterlander

--- In QuadtoneRIP@yahoogroups.com, Ernst Dinkla <E.Dinkla@...> wrote:
>
> fwaterlander wrote:
> 
>   When I convert an
> > RGB image to grayscale and apply Levels to set the black and 
white 
> > points, the resulting contrast is significantly less than when I 
stay 
> > in RGB mode, desaturate and apply Levels to set the black and 
white 
> > points. After Convert to Profile, save as tif and print with QTR 
this 
> > difference in contrast clearly shows in the prints.
> 
> LIke mentioned by others I would suggest to use the channel 
> mixer in PS and convert to grayscale there with the PS color 
> settings combinations: AdobeRGB - gamma 2.2 or sRGB - gamma 
> 1.8 for greyscale. There shouldn't be a change in contrast or 
> gamma then. Check the values with the L(ab) window in Info. 
> There could be some visual shifts at the ends when colors are 
> pronounced at the ends of the range and they convert to 
> lighter or darker tones with the channel mixer settings. At 
> least you have control with this method. Any other tone 
> corrections can/should be done in greyscale afterwards and the 
> image saved as such with gamma 2.2 for example. Just for 
> printing the conversion to the suitable QTR 
> printer/matte/gloss/paper profile is used and the image is not 
> archived but goes in the bin after printing. Where I have 
> written gamma 2.2 you could use QTR Gray-lab profile instead.
> 
> If you use PWP as an image editor then all bets are off when 
> you do conversions to QTR profiles. In general there are some 
> flaws in its CM whether you select Microsoft's color engine or 
> the LCMS engine. If you print through Qimage you better stay 
> in RGB when the QTR (RGB) profiles are used in Qimage's CM or 
> switch the CM off and load a printer ready (prepared in PS) 
> image in Qimage.
> 
> 
> Met vriendelijke groeten,  Ernst
> 
> 
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