Digital BW, The Print

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, Peter Miles <P.Miles@m...> 
wrote:
> 
> 
>  Peter Miles wrote...
> 
> > I've recently installed Roy Harrington's QuadTone Rip 2.0
> > 
> > Running set-up tests with..
> >  PizeoTone selenium inks
> >  Epson Matt Heavyweight [A3]
> >  Quad Tone Rip 2.0
> > 
> > 
> > WOW - The results are stunning!,  However the photographer
> > whose work I've been printing commented on what appeared to be slight
> > 'tonal' banding running down the length of the print. Bands are about
> > 30-35mm apart.
> > 
> > I checked prints made from the same file printed using the Cone driver - no
> > banding. 
> > 
> > While we were looking at the print to see what it was I Turned the print
> > over and we could see the same banding pattern on the back of the print! On
> > closer inspection we saw the print paper (Epson MHW) had *very* small but
> > regularly spaced 30-35mm wide corrugations running down the entire length of
> > the print. These corrugations are easier to feel than to see directly.
> >  
> 
> 
> 
> Roy Harrington wrote...
> 
> > I'm having a hard time understanding what you are actually seeing.
> > So the pattern goes down the paper not along the head direction?
> 
> Yes, that is correct.
> 
> 
> > I'm also not sure about "very small" and "30-35mm"  which sounds very large.
> 
> Sorry I was a bit vague. The spacing between corrugations is 30 - 35mm but
> the depth of corrugations is very small.
> 
> This means that the print surface is not quite flat. The varying print
> viewing angle seems to cause very slight variations in the appearance of the
> print tone values. On the print, this slight variation becomes apparent in
> areas of very flat print tone such as cloudless sky.
> 
> 
> > Is it possible to see it with a scanner, so you could show it?
> > How you tried other kinds of paper?  I don't think HWM is recommended
> 
> We found Epson Archival Matte paper ripples to a lesser extent than Epson
> MHW 
> 
> 
> > for pigment inks -- maybe there's just too much ink for the paper to absorb.
> 
> I pretty sure this is the real problem.
> We have run more tests last night and some more tests this morning.
> The regular pattern of ripples correspond with the gaps between the top
> pinch rollers of the 1160. I think the paper is swelling with the ink and
> the only place the print can buckle is between the gaps between the top
> pinch rollers, This seems to be the cause of the regularity of the ripple
> pattern.
> 
> Is there something in  my "quadtone curve descriptor file" That would cause
> excessive ink loading?
> 
> <Snip-ink limits>
> LIMIT_K=85
> BOOST_K=100
> LIMIT_C=100
> LIMIT_M=95
> LIMIT_Y=95
> 
> <Snip-Gray Partition Information>
> N_OF_GRAY_PARTS=4
> GRAY_INK_1=K
> GRAY_VAL_1=100
> 
> GRAY_INK_2=C
> GRAY_VAL_2=30
> 
> GRAY_INK_3=M
> GRAY_VAL_3=5.05
> 
> GRAY_INK_4=Y
> GRAY_VAL_4=2.86
> 
> GRAY_HIGHLIGHT=11
> GRAY_SHADOW=11
> 
> GRAY_OVERLAP=50
> GRAY_GAMMA=1
> GRAY_CURVE=
> 
> 
> 
> > Other alternatives are to try different "Image Types" and "Dither Algorithms",
> > you may get different results.
> 
> We found printing faster (1440x720 bidirectional) reduced the depth of the
> ripples somewhat [without any change in print quality].
> > 
> > Roy

Peter,

Looking at your parameters here I'd say you are really over saturating
the paper. I have an 1160 -- although it's a VM ink set not a quad set
such as piezo.   First your ink limits seem very high.  I use limit=70 with
the boost_k up to 90 or 100.  So K,C,M,Y = 70 and BOOST_K=100.
Second the GRAY_OVERLAP is very high -- basically meaning 150% of the
ink (based on their ink limit).   I use GRAY_OVERLAP=0 now.  Once
you change these values you won't have such huge dot gain and the
GRAY_VAL numbers will need to change.   You should do the ink calibration
again with these lower ink limits and I'd expect instead of 30, 5, 2.8  they
will be more like 45, 10, 5.  

Roy