QTR-Quadtone RIP

First, I have never noticed a loss of contrast when converting a
desaturated image to grayscale. Second, when the documentation was
written, QuadtoneRIP required a grayscale tiff as input. That has
since been relaxed.

Tom Moore

--- In QuadtoneRIP@yahoogroups.com, "Frans Waterlander"
<frans2001@...> wrote:
>
> Tom,
> 
> Thanks for your reply. I'm well aware of the different ways to 
> convert an RGB image to grayscale mode. However, conversion to 
> grayscale mode, at least to the best of my knowledge, causes a loss 
> of contrast as compared to maintaining the RGB file as an RGB file 
> and using Desaturate or Channel Mixer/Monochrome in Photoshop. So why 
> does the QTR documentation suggest you convert to grayscale mode? QTR 
> works just as well on RGB mode Desaturated or Channel 
> Mixer/Monochrome images as long as you use Convert to Profile/QTR - 
> RGB Matte Paper or /QTR - RGB Photo Paper before saving as tif.
> 
> Frans Waterlander
> 
> --- In QuadtoneRIP@yahoogroups.com, "Tom Moore" <rtmlists8888@> 
> wrote:
> >
> > Frans
> > 
> > The issue of conversion from colour to B&W is a complex one that has
> > engendered many long debates and discussions. A companion list to 
> this
> > one, DigitalBlackandWhitethePrint has had several useful discussions
> > on this point. Also, there are many tool for B&W conversion 
> providing
> > many options for contrast and conversion of various hues to 
> different
> > tones.
> > 
> > The main reason for conversion to greyscale is not so much to reduce
> > file size, but rather to map colours in your image onto different
> > parts of the tonal range. The resulting image can still be an RGB 
> file
> > or a greyscale file. Generally they should both appear and print 
> the same.
> > 
> > The least favoured way of conversion is the PS Convert to Greyscale.
> > Desaturation of an image is often an improvement but doeson't offer
> > much flexibility. Another method with more flexibility is using the 
> PS
> > Channel Mixer although I don't find it very convenient to use.
> > Currently I often use the so-called Gorman technique. A PS script 
> for
> > it and a number of other conversion techniques can be found here:
> > 
> >    http://www.atncentral.com/download.htm#BW_Conv
> > 
> > Tom Moore
> > 
> > --- In QuadtoneRIP@yahoogroups.com, "fwaterlander" <frans2001@> 
> wrote:
> > >
> > > "Conventional wisdom" for QTR seems to be to work in grayscale 
> mode, 
> > > but QTR also allows to work in and save in RGB mode. 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.
> > > 
> > > So my question is: why would I ever want to convert to grayscale 
> mode 
> > > given these results, particularly since all my images are in RGB 
> mode 
> > > to begin with. And yes, I can always increase contrast after 
> converting 
> > > to grayscale, but why do this in the first place?
> > > 
> > > Because storage space is so cheap these days, the argument that 
> the 
> > > resulting grayscale files are smaller is not a very valid one in 
> my 
> > > opinion.
> > > 
> > > Frans Waterlander
> > >
> >
>