QTR-Quadtone RIP

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


|  Dinkla Grafische Techniek  |
|     www.pigment-print.com    |
|             ( unvollendet )            |