QTR-Quadtone RIP

I put the question in two lists here first. The Qimage forum often is 
less B&W interested and isn't always responding nicely on bug reports. I 
wonder who shares the same experience I describe below. Forget the Z3100 
driver mentioned here, it should be the same problem with Epson or Canon 
B&W driver modes.

So far my B&W printing has been on matt papers that do not have a Dmax 
above 1.8. For a long time I didn't trust Qimage's handling of the QTR 
ICC profiles in particular its BPC interpretation. So with the 9000 quad 
I had I would first do a P2P conversion to the custom QTR paper profile 
in Photoshop before using Qimage to set multiple scaled prints on one 
print page and print to file and from there with QTR. That worked 
properly (but slow) and I kept that method even after some messages 
appeared that Qimage was compatible (again) with the QTR ICC profiles. 
Didn't print other than matt paper in practice.

After I got my HP Z3100 I changed to printing from the Advanced B&W (HP 
gave it another name though) mode in the driver  and used custom QTR 
paper profiles (RGB) in Qimage color management to make sure that it had 
the right perceptual tone range. Perceptual rendering with BPC on. Still 
on matt papers. Dmax around 1.7 on HPR Bright White, a very slight drop 
from the target's Dmax I made the profiles with.

Over the last two weeks I changed the Z3100 firmware + driver to the 
latest version and upgraded to Qimage's Studio version 2007.178. Thought 
it was time to make some QTR profiles for the Innova fiber paper and HP 
gloss + satin versions of Premium Instant Dry. I have made several 
profiles for HP Premium ID gloss with color management off in Qimage 
(the driver has CM off as the default in my preferred settings) using 
the Advanced B&W mode of the driver (on neutral) with the optimal 
setting + GE all over the print. Dmax varies between 2.249 (5.09 L) for 
the step 21x4 random target, 2.265 (4.91L) for the step 51 random 
target. Nice results.

Printing from Qimage however with CM and Perceptual + BPC on cut the 
Dmax back to between 1.98 - 2.05. Whatever method chosen: with a 
greyscale QTR profile, the RGB QTR profile and both used on greyscale 
and RGB versions of the 21 + 100 step wedge (2.2 Gamma).  If I used the 
same profiles and wedges in Photoshop with a P2P conversion with 
Perceptual + BPC and printed that through Qimage (with CM off) I got a 
2.2 Dmax value on average. That's OK with me and tells me something is 
still not working in Qimage. Suspecting the BPC function again I put two 
targets on one print page in Qimage and used CM with Perceptual 
rendering, one target with BPC on, the other with BPC off. Qimage allows 
custom profile settings per image on one print page. That made it clear 
that BPC on cut the Dmax, one measured 2.2 the other 1.98.  It probably 
only happens or gets only visible with Dmaxs above 2.0 D.

To dampen any comment about using CM on in the application and using QTR 
profiles with that while the Z3100 Advanced B&W instructions say to set 
CM off in the application you print from: I see better shadow separation 
and better highlight build up with the QTR profile (working properly: PS 
P2P) than any other setting with the Advanced B&W mode: CM in 
application off or with CM on and a normal custom ICC profile used. So 
HP's recommendation isn't the best and the color profile (based on the 
color mode printed target so not entirely correct for this setting) 
isn't good either. Printing in color mode and with custom color profiles 
takes out some Dmax already in the target, the ABW mode gives more Dmax 
usually so for me that's no option either. And as written I get 
suspicious about Qimage's BPC for color as well when a Dmax above 2.0 is 
possible.

For the time being I will print B&W gloss either with PS and the QTR 
profile (best tone rendering) or through Qimage with CM off in Qimage = 
Z3100 driver B&W rendering being second best. Qimage's CM perceptual 
with and without BPC isn't correct.

Roy, is this the spec of the profile (v4 ICC, and then coder's taste for 
BPC algo) or something more fundamental. Mike has written more comments 
on BPC and doesn't see Adobe as the standard to refer to. Cutting 0.2 D 
from 2.2 Dmax is not something I see as a difference of taste though. Or 
has it something to do with the a b data in the profile and Qimage's 
effort to get near neutral black in line with neutral black in the 
shadows ?  Something that is important in color printing but with a b in 
the QTR profiles not playing a role in color toning  with B&W printing 
it should be blocked to influence BPC too. Anyway: PS does it correct.


-- 
Met vriendelijke groeten,  Ernst

 
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