QTR-Quadtone RIP

Roy Harrington wrote:


> In general this might not seem possible and probably wouldn't work, but 
> with
> QTR profiles this works quite well.   The first key issue is that the 
> curves that
> you blend are all linearized the same way.  Dmin and Dmax in general are
> identical and all the L values in between are the same for the same 
> grayscale
> value.  This makes the weightings always between the same density.  The 
> other
> key issue is that the weightings are calculated deep in the driver 
> where the
> exact amount of ink is known.   

Roy,

I take your word for it that it workes. It is correct that I 
assumed more complexity.

With the lines you write above I have another question: As you 
know Steve Kale is using your profile creation appl for the 
Epson K3 ABW driver. He wrote me that he creates them on 
mainly the default setting but a profile for every hue shift 
he normally uses. That means more profiles per paper and the 
advantage of soft proofing in Photoshop. The limited hue 
choices a B&W photographer uses in practice will reduce the 
number of profiles as has been mentioned before. In that way 
Steve's, David's and your approach are not that different. I 
expected more flexibility in Steve's method but it isn't.

I wonder whether it is possible to make just one general 
greyscale profile per paper with your application based on 
averaging 3 or 4 target measurements, each target made with a 
hue at the boundaries of the gamut one uses in B&W printing. 
Choices made with the ABW driver but when your QTR gets the 
same flexibility (sliders etc) it would work there too. I'm 
actually thinking of the HP Z3100 ABW driver. That 
averaged-general profile represents the average luminance 
scale of that small gamut used. It will not work for soft 
proofing color but I think the preview/softproof of the ABW 
drivers will be sufficient for hue selection. The P2P 
conversion can be done before the image is brought to the ABW 
driver/preview if the  ABW viewer isn't ICC profile 
compatible. My goal is to reduce the quantity of profiles as 
just one per paper and keep the flexibility of the ABW drivers 
in hue choice.

Do you foresee visible shifts in the luminance range with the 
different hue choices even when that gamut is limited ?  Of 
course much depends on right averaging within that small gamut 
space.

Met vriendelijke groeten,  Ernst


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