QTR-Quadtone RIP

Roy Harrington wrote:
> Ernst,
> 
> When I first tried Qimage with QTR ICCs back over a year ago there were some
> issues.  The issue was a combination of both Qimage and Little CMS which is the
> internal color management of Qimage.  At the time we got things to work just
> like they do Photoshop.  I guess it's possible that it has been broken
> in a later
> version -- (I don't use Qimage on any regular basis so I wouldn't find
> out about it).
> 
> The whole BPC issue is a problem in general.  It is not addressed in
> the ICC standard
> at all -- neither v2 or v4.  To quote the website it's "under active
> consideration".
> Adobe is the one who initiated the concept and wrote the "standard" for it.
> Another issue is that rendering intents are also up to implementers --
> the idea is
> specified in ICC but the exact math involved is not.
> 
> It's easy to see what your particular setup does.  Instead of printing
> the output of
> Qimage (or any other program) send the output to a tiff file and open it up back
> in Photoshop to see what's been done to it.  Use a 21 stepwedge and look at the
> histogram before and after -- or even just a 100% black box.
> 
> Roy

Roy,


There's an older Qimage mailing list comment by Mike on BPC 
where he writes that BPC is not needed in perceptual 
rendering as the last already compresses the total within 
the printer's gamut. So he advises to keep BPC on in both 
perceptual (not doing harm) and relative colormetric (needed 
there for good shadow rendering). True if it works correctly 
but I see differences in Photoshop Perceptual rendering with 
and without BPC. In Qimage it certainly isn't inactive in 
the case I sketched.

I rather print samples to really see and measure what I get 
than check it in PS that needs to be treated carefully  as 
CM is almost never really suppressed in that program. 
Picture Window Pro's CM can be switched off totally, on the 
other hand that application has a quirky CM when switched on :-)
I have been testing all the applications on QTR ICC 
compatibility probably two or three years ago and PWP made a 
mess of it then and now, Qimage is back to an old problem it 
seems but worse now as I want to print gloss with the higher 
Dmax.

I'm going to measure the targets I got and select the method 
with the tone range that comes near the ideal curve for that 
Dmax. If the HP ABW sans application CM isn't too bad I 
might use that with Qimage for the time being, the QTR 
profile did correct the tone range though but I do not want 
to print from PS.


Met vriendelijke groeten,  Ernst


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