Digital BW, The Print

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