QTR-Quadtone RIP

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

On 6/18/07, Ernst Dinkla <E.Dinkla@...> wrote:
> 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
>
>
> |  Dinkla Grafische Techniek  |
> |     www.pigment-print.com    |
> |             ( unvollendet )            |
>