QTR-Quadtone RIP

To prove that I've gone compulsive-obsessive, here are results with
the modified QTR-Create-ICC-BPC.exe using my standard test image:

   http://www.ferdinand-paris.com/BPC-Qimage_V4.png

It confirms what Roy says - that profiles created with it are
well-behaved in Qimage with or without BPC. Well, well behaved up to a
point - the Qimage CM still produces spikes in the darker end of the
histogram, but I don't think that's the fault of the profile.

@Roy:  I have been thinking about what I said in my last post - that I
don't find the softproof with my custom profile (the one made with the
normal version of QTR-Create-ICC) particularly reliable.  I did some
tests.  

I opened in PS an output file from Qimage that shows the big dMax loss
after conversion to a "normal" custom profile.  I also opened the
original sRGB file in PS and soft-proofed using the the same custom
profile.  I turned off simulate paper colour for this comparison.  As
I was using perceptual, BPC did not make an impact.  If I turned on
"Simulate Black Ink" then the two images appeared to be the same on
the screen.  Thus it appears to me that Qimage is reading the
information required to simulate the ink black in a soft proof as a
BPC to be applied in conversion.

Of course the same test can't be done with new custom profiles made
with QTR-Create-ICC-BPC.exe, because you've turned "Simulate Black
Ink" off, and so Qimage is not confused by it.  I assume that's why
you turned it off.

I tried this test also with a 21 step wedge with the same results. 
The output from Qimage (perceptual + BPC conversion to a "normal"
custom profile) looks the same on screen as the original step wedge
soft-proofed from 20% grey into my "normal" custom profile with
"Simulate Black Ink".  I.e.  it appears that Qimage is again applying
the soft-proof black point simulation when converting with BPC.  Black
0 becomes luminance 26.

Getting back to where I started, I don't find this soft-proof all that
convincing.  It's convincing in terms of what Qimage produces with a
"normal" custom profile + BPC, i.e. of a large dMax loss.  But not of
what I get if I print from PS, nor if I convert in PS and print from
Qimage without CM.

In summary, the "Simulate Black Ink" soft-proof adjustment seems too
large and seems to be misinterpreted by Qimage if it's in the profile.

I hope this helps and makes sense, and doesn't demonstrate too many
fundamental CM misunderstandings.

F_P


--- In QuadtoneRIP@yahoogroups.com, "Roy Harrington" <roy@...> wrote:
>
> I've got a new version of Create-ICC that might help in this.
> 
> Download:    http://www.quadtonerip.com/QTR-Create-ICC-BPC.exe
> 
> This maps black to black on both directions of the profile.  What 
> this gives up is soft-proofing with Simulate Ink Black.  The benefit
> though is my tests with Photoshop show identical results for all 
> combinations of Perceptual & Relative Intent and BPB on or off and 
> with different CMSs on the Mac.
> 
> I'm interested in any findings you guys get.   I highly recommend 
> using a 21step wedge to do this.  Cut out just the steps so you have
> a perfect comb in the histogram.
> 
> Then you can see if the results are the same.  (+/- 1 level is OK). 
> With PS I used 16bit and the histo-results were 100% identical.  
> I'd also go with a simple made up custom profile such as "20 96"  
> which shows significant movement in the histo.
> 
> Roy