QTR-Quadtone RIP

There's really only two dithering methods that I think are worth looking at.
They are Ordered and Adaptive Hybrid.  From looking at the code both Floyd
and Eventone just do Adaptive Hydrid.  Fast and Very Fast aren't that good as
far as I can tell.  

The results from Ordered and Adaptive are pretty close -- they are different but
overall give similar results.  On any given image there may be visible differences
but I had a hard time conclusively saying one was clearly and always better than the other.
Early on I remember seeing an occasional yet rare artifact in the Adaptive dither
on specific test prints - not real photos.  That combined with the noticeably faster
algorithm for Ordered, I always use Ordered.

Ordered dither is the only one that I can say I mostly understand.  There seem to
be some docs that imply that it doesn't do well with variable dot sizes.  I don't in
general find that to be true but I have been experimenting with the handling of
variable dot sizes.

Roy


--- In QuadtoneRIP@yahoogroups.com, "Olivier" <odesmais@y...> wrote:
> Based on this 3 links :
> 
> http://gimp-print.sourceforge.net/developer-html/gimpprint_26.html
> http://man.digipedia.pl/man/man7/gimpprint-dithers.7.html
> http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=00BR5g
> 
> it's very hard to find out the effects of each dithering methods 
> (except "fast" and "very fast" are not adapted to fine BW prints).
> 
> The thread from photonet states that only ordered,fast and Adaptive 
> Hybrid are implemented in QTR ?
> 
> The one from sourceforge seems to recommend Adaptive Hybrid since 
> ordered is only preferable for 4colors none variable dot sized 
> printers, A/H would use error diffusion in dark & halftones and ordered 
> in light tones.
> 
> 
> None of these papers is too explicite. Any additonal comments from 
> better experimented people than me...
> 
> Olivier
> 
> 
> --- In QuadtoneRIP@yahoogroups.com, "Olivier" <odesmais@y...> wrote:
> > John, thanks for the below. In fact I'm looking for an explanation of 
> > how the different dithering methods calculate the print and the 
> > difference between each.
> > 
> > Olivier
> > 
> > --- In QuadtoneRIP@yahoogroups.com, "John Moody" <moodymz3@y...> 
> wrote:
> > > The reply has not changed, but I have been using eventone for matte 
> > paper at
> > > 1440 super, and ordered for luster at 2880 dpi with the R200 
> printer.
> > > 
> > > Best regards,
> > > John Moody
> > >