QTR-Quadtone RIP

Mike,

I must say I have never ecountered posterization issues with customary inks that use K, LK, and LLK alone, or as backbone followed by LM, LC, and others for toning via use of "toner" or "copy curve from" in QTR ink setup.

I think Cone type overlap may (perhaps) be required when using 4+ gray inks, which in my opinion is at best an overkill, and technical mas@#$%^tion at worst. I have not seen a print that was better simply because it had 6 or 7 shades of gray. Try to reduce the number of gray inks in your set up, and use standard QTR curves design tools. I am curious what your eyes will see.

Shilesh

Shilesh

--- In QuadtoneRIP@yahoogroups.com, Michael King <drmrking@...> wrote:
>
> Roy,
> 
> >>If you have posterization issues it's almost certainly due to other
> issues.
> More bits and more overlap are pretty much the very last things to be
> concerned about. Posterization is usually in the image or you have bad inks
> 
> So all I can say is that I have a image that posterizes with QTR curves
> (limited overlap) but not Cone style overlapping curves. Same inks, same
> printer. Solved the problem by using using overlapping curves and
> linearizing with my own spreadsheet based linearization tool. This 7 ink set
> up is using a mix of HP-PK and Eboni MK (18% & 100%). It may have been
> caused by some other effect that I removed by using overlapping curves, but
> there is no doubt that overlapping curves solved the problem, whatever is
> causing it.
> 
> Mike
> 
> 
> 
> 
> On 29 March 2010 19:00, Roy Harrington <roy@...> wrote:
> 
> >
> >
> > On Mon, Mar 29, 2010 at 9:02 AM, Michael King <drmrking@...<drmrking%40gmail.com>>
> > wrote:
> > >>>Is there any benefit in re-creating custom curves for this new version?
> > I
> > > have just finished profiling two papers for QTR and wonder if they would
> > be
> > > a) compatible, b) have greater accuracy with this new version?
> > >
> > > As I read in Roy's answer to my earlier question - there has been no
> > change
> > > to profiling. Its still 8 bit based. BUT he is interpolating between the
> > 8
> > > bit values to generate intermediate values to support 16bit.
> >
> > There have always been 256 points in the QTR curves but the values at each
> > of the points have always been 16-bit. The 256 points are already way
> > overkill
> > compared to, for instance, color ICC profiles. ICC color management
> > typically
> > uses interpolation with just 25 points so QTR curves have 10 times that.
> > Interpolation is a perfectly good technique.
> >
> >
> > >
> > > To be honest paper coatings are barely consistent enough across the page
> > to
> > > let you profile at 7 bits (128 values) never mind more than 8 bits. So we
> > > would be able to gain nothing from Roy directly increasing the curve
> > > resolution beyond 8 bits.
> > >
> > > You might ask what's the benefit of 16 bit printing ? Well I expect the
> > main
> > > benefit is in helping smooth tonal areas avoid posterization, by creating
> > > more ink values in the tonal graduation.
> >
> > If you have posterization issues it's almost certainly due to other issues.
> > More bits and more overlap are pretty much the very last things to be
> > concerned about. Posterization is usually in the image or you have bad
> > inks.
> >
> > Roy
> >
> >
> > >
> > > I've been wrestling with this issue for the last few months and have been
> > > experimenting with Cone style overlapping curves and QTR less overlapping
> > > style. There is no doubt more overlap reduces the problem BUT also for
> > some
> > > papers overlapping curves reduces dmax. So as usual there is no free
> > lunch.
> > > I am excited about the potential of 16 bit printing to address this issue
> > -
> > > just got to Hackintosh my PC first :)
> > >
> > > Mike
> > >
> >
> >  
> >
> 
> 
> [Non-text portions of this message have been removed]
>