QTR-Quadtone RIP

The linearization inside of QTR is to make the driver produce 
consistent, smooth gradients.
It's also crucial to the Tone Blending so that density variations don't 
occur.
While the ICC profiling resembles this linearization, it provides color 
management info to
match screen to print.  Without it the embedded profile of the image 
would be ignored for
printing but not for the display.  It also allows to CM system to map 
the idealized gray working
space into the actual dMax and dMin in the way that gives the best 
"perceptual" feel of the print.

The issues of using various intents and black pt comp are not as well 
defined by the ICC standard
as you might think.  Lots of details are left to the implementer.    
The basic math for QTR ICC
profiles is based on perceptual intent and bpc as published by Adobe 
(not ICC btw).
Take a swatch of pure black and try various combinations of Convert to 
Profile and you'll see
that some don't maintain the pure black.   My recommendation on 
Perceptual and BPC is based
on trying various ways and seeing that this is the most consistent.

Roy

On Thursday, August 24, 2006, at 08:41  PM, Jeff Kohn wrote:

> You know the more I think about this, it seems like maybe the 
> linearization within QTR is already a kind of perceptual rendering, 
> since it re-maps the curve to given you a smooth, even transition from 
> black to white (0 to 100). In that case maybe by converting to the ICC 
> profile with perceptual intent, in a way you're double-profiling?
>  
>
> Jeff
>  
>
<image.tiff>
>
> From: QuadtoneRIP@yahoogroups.com [mailto:QuadtoneRIP@yahoogroups.com] 
> On Behalf Of Roy Harrington
> Sent: Thursday, August 24, 2006 11:45 AM
> To: QuadtoneRIP@yahoogroups.com
> Subject: Re: [QuadtoneRIP] Re: Printing with ICC profiles
>
>
> Hi Jeff,
>
> If you are seeing a drop in dMax using the ICC profile, the profile
> conversion is probably being
> done incorrectly. It sounds like RelCol conversion instead of
> Perceptual.
>
> I can't tell whether you are on a PC or Mac but Photoshop often
> defaults to
> Relative Colormetric conversion rather than Perceptual Intent. Be
> sure to double check that you
> are using Perceptual and using Black Point Compensation.
>
> Roy
>
> On Wednesday, August 23, 2006, at 11:01 AM, Jeff Kohn wrote:
>
> > From what I'm seeing so far, I think it's best to just use the ICC
> > profiles for soft-proofing and not printing. I'm finding that 
> printing
> > an image using the "QTR Gray Lab" profile yields better results than
> > using a Create-ICC generated profile with perceptual intent. The
> > latter lightens the print noticeably, and really kills the DMAX of 
> the
> > print (dropping it from 1.6 to 1.3 in the case of my custom curve for
> > Hahnemuhle Photo Rag that I'm currently working on).
> >  
> > I've been meaning to post a discussion about this and will try do so
> > in the next few days. First I want to finish tweaking my custom curve
> > and do a bit more testing/measuring.
> >  
> > Jeff
> >  
> >
> <image.tiff>
> >
> > From: QuadtoneRIP@yahoogroups.com 
> [mailto:QuadtoneRIP@yahoogroups.com]
> > On Behalf Of dlruckus
> > Sent: Wednesday, August 23, 2006 12:37 PM
> > To: QuadtoneRIP@yahoogroups.com
> > Subject: [QuadtoneRIP] Re: Printing with ICC profiles
> >
> >
> > Hi Joe.
> > You need to convert to profile before printing.
> >
> > Regards
> > Duane
> >
> > --- In QuadtoneRIP@yahoogroups.com, "joemulligan_68"
> > <joemulligan_68@...> wrote:
> > >
> > > Since the Yahoo search is not the most efficient, I hope to ask 
> this
> > basic question:
> > >
> > > How do you print using icc from QTRgui?
> > >
> > > I have been successful with the Create ICC program while printing 
> on
> > Mac but since I am now
> > > running bootcamp and Windows, how do I go about this with QTRgui?
> > >
> > > Should I Assign Profile to the file and then print? Or should I
> > Convert to Profile?
> > >
> > > A bit confused at the moment. Thanks to all in advance.
> > >
> > > JoeM
> > >
> >
> >
> -
> Roy Harrington
> roy@harrington.com
> Black & White Photo Gallery
> http://www.harrington.com
>
>
-
Roy Harrington
roy@...
Black & White Photo Gallery
http://www.harrington.com