QTR-Quadtone RIP

--- In QuadtoneRIP@yahoogroups.com, Ernst Dinkla <E.Dinkla@c...> wrote:
> 
> >
> >There are really two parts to what you see on the paper.  Dithering is the decision of
> >where to put all the dots on the page.  This always happens in the driver in your
> >main computer not in the printer.  So for this QTR and Epson are completely different.
> >The second stage is typically called "weaving" or "interleaving".  This is deciding which
> >physical jet in the head will print each dot.  On the Pro printers like the 4800 this is
> >done in the printer so the Epson driver and QTR will use the same code.  On the 
desktops
> >this function is in the driver so QTR and Epson driver are different.   I'm really not
> >sure what is being reported as "better dither".  I think another possibility is that the 
"better" 
> >they are seeing is just the effects of the light-light-black ink rather than the dots.
> >



> 
> Roy,
> 
> I'm quite sure Epson information mentioned something about other weaving 
> methods or alike. Will try to find it.
> 
> Ernst

The weave methods vary a bit based on resolution, but on the usual 1440x720 its mainly
just a choice of 4 pass vs 8 pass (in QTR 1440dpi vs 1440super).  What this means
is how many different jets are used on one horizontal line.  The idea is to cover up
small variations in jet size and position.

> In the Stylus Pro 4800_4800.pdf (Stylus Pro 4800 Brochure) the following 
> is written about the Black and White specs: Proprietary Epson Screening 
> Technology developed specifically for black and white printing. Maybe 
> interpretable in more than one way: is it how the dots are placed or is 
> it referring to partitioning ?
> 
> At the start of the brochure a technology is mentioned: Proprietary 
> Active Meniscus Control AMC precisely controls the curvature of every 
> ink droplet within each nozzle before releasing it into the media. the 
> result is extremely sharp and accurate placement of ink droplets for 
> outstanding photographic print quality.
> That doesn't indicate new weaving but can explain better droplet 
> formation with old weaving routines. All done at printer 
> hardware/firmware level though. The Pro range always had more consistent 
> droplet sizes and placement than the desktop models. And probably 
> related to that: larger minimum droplet sizes.
> 
> Wonder how they do the meniscus measurement and how the correction 
> within the short time possible is executed ?  Measuring different 
> conduction at the nozzle surface, reflection of the surface while the 
> droplet is formed, acoustic measuring ?  It is not the fact that it can 
> be done but at this speed and that it will work in an environment with 
> ink flying around for months that amazes me.
> 
> Ernst

I don't know for sure what this AMC is but here's my guess.  The major issue to
deal with to get smooth results is the physical variation of the 180 jets/ink.  That's
a lot of jets and manufacturing tolerances can go so far.  The major solution has
been the weaving methods (as above).  As long as you vary which jets are used on
a line there's less chance the one jet that is off (bigger or smaller) will show to the eye.  

My guess is that in the factory they just measure all the jets to see the variation.
This sounds complicated but the auto nozzle check does much of what you need.
Each patch is printed with only one nozzle so you can measure the density of each
patch to get an idea of the nozzle variation.  Then you burn into the firmware a
table of the variations.  At print time, you give a "big" nozzle a little less voltage and
a "small" nozzle a little more voltage.  Overall you ought to be able to reduce the
variation of nozzle dropsizes.  Just a guess but it fits the description.

> Joseph Holmes has this on screening of the new Pro models:
> 
> 8) The screening technology has been overhauled for color, to 
> accommodate the improved precision of the new print head. The screening 
> for the Advanced Black & White mode is of course all new and does an 
> amazing job of creating consistent coloration throughout the tone scale 
> and superb smoothness on photographic papers (e.g. Premium Luster). 
> Smooth results on rag papers are much easier to achieve.
> 
> 
> Ernst

The B&W mode obviously uses less color inks just like QTR has always done.
Smoother is by far a result of having and using the light-light-black ink.
These ARE very good improvements and worth touting for in the 
standard Epson driver.

Roy