Digital BW, The Print

--- In DigitalBlackandWhiteThePrint@y..., "Martin Wesley" 
<mwesley250@e...> wrote:
> 
> ----- Original Message -----
> From: "jimhayes361" <jimhayes@j...>
> To: <DigitalBlackandWhiteThePrint@y...>
> Sent: Wednesday, March 13, 2002 5:03 PM
> Subject: Re: [Digital BW] k microbanding 1280 w/ VM
> 
> 
> > --- In DigitalBlackandWhiteThePrint@y..., "Martin Wesley"
> > <mwesley250@e...> wrote:
> 
> (snip)
> >
> > Yes, it has only started doing it today. I have a print with LOTS 
of k
> > in it, like 92-98%k. I printed it a few weeks ago, no problem,
> > beautiful. I compare it to a print done today, same settings,
> > everything else the same (btw I'm using curves I got from Paul for
> > printing at 2880 dpi- so I'm at that resolution printing this both
> > times)- cordury. It vanishes lighter than about 90%k.
> 
> Jim,
> 
> The k seems to be the most troublesome ink in the VM set. I have had 
it fade
> out in the middle of 13x19 print on $4 per sheet paper and then come 
back in
> towards the end.

It clogs much more. When you look at the instructions for mixing your 
own quads at the MIS site, the graph indicates just a few drops or so 
of pigment will get you a bottle of the lighter colors, but to mix a k 
bottle a signifigant proportion is the pigment added to the clear 
base. Interesting reading. 


 
> 
> I thought that there is probably more back pressure on the CIS than 
the
> cartridges due to the need to pull the ink the extra distance from 
the
> bottles. After refilling my yellow bottle and printing a purge page 
I was
> amazed at how quickly the yellow was sucked into the tube and I have 
the
> extra long tubing to put the bottles behind the printer. 


I'm guessing that it's  a vacuum action...as ink gets drawn through 
printhead it pulls on liquid in bottle. Raising or lowering the 
bottles has a secondary effect (another guess) in creating a pressure 
head.

If the scenerio is correct, the thing that would kill a CIS/CFS is an 
air leak at either bottom of printhead, between cart and printhead, or 
in tubing from cart to bottle. Vacuum would be broken as air is sucked 
in instead of ink.

Just having carts has the same two actions I expect- how much head is 
left in cart and keeping air out. But (another guess) head is more 
important than air leaks- it doesn't have to pull a vacuum on an ink 
source that is two feet away.

Fluid Dynamics was NOT my best subject, and it was over 25 years 
ago<g>.

Anyway, I'm starting to think that in a non-CIS system, the carts are 
not as sensitive to ink level as I once thought. There may be more 
tendancy to clog, esp in k cart, when it gets low, like about 10% 
left.
 

> >
> > It's visable a good foot away under a good quality Ott-lite, no 
loupe.
> > Very apparent when comparing to print I did some weeks ago.
> >
> > But we may still be talking borderline maybe for most folks.
> 
> Well that sounds like it is on the edge of acceptability but no two 
sets of
> eyes are the same.
> >
> (snip)
> >
> > I'll show it to a person or two and see if they catch it.
> 
> My wife is always my victim for this and other comparisons. The 
standard
> answer is , "What difference? Are you nuts, they are identical." 
Helps me
> form my own opinions one way or the other.

My wife can't detect it either. She can spot even moderate DSS clearly 
 but not this. It is there, but I'm leaning towards dropping the whole 
thing and just enjoying doing art, you're absolutely right about 
letting it go at some point. It's noise level.

We did figure out that the print done a few weeks ago was a little 
lighter in shadow areas. This probably means I printed it at 1440 dpi 
using Pauls regular VM curves posted on MIS website. The one I did 
last night, was done at 2880 with special curves, that print a bit 
darker in the shadows which works well for my tastes on this paper.

If that is the case, when a lot of k is present, I ought to print at 
1440 dpi- slightly smoother than 2880. I know that is 
counter-intuitive, but I'm going to run the print again at 1440 to 
test it out.

> >
> (snip)
> >
> > Nozzles checks great before and after. I even take 
loupes/lighttables
> > to my nozzle checks when in doubt- these look fine.
> 
> Have you tried a different paper? I wonder if some of this is not 
related to
> variations in the paper receptor coatings.

I can switch from Eclipse Satine to Legion Photo Matte, say. But I 
think it has something to do with my special "2880 curves" when they 
try to print dark. But again, I'm starting to not worry about it much.

> >
> > But I think it would be wise to do an alignment, although the 
lines
> > are parallell to shorter edge.
> 
> How do you go about assessing the alignment squares on second part 
of the
> 1280 alignment procedure? The differences are pretty easy to see 
with color
> inks but with gray scale it is tough.

This is the one beef I have about the 1280 printer. What I've been 
doing is popping an Epson cart in whenever I change paper, and 
hopefully only doing it when I run out a virgin vacuum filled cart. 
The Epson cart also clears the plumbing a bit, so that's nice too.
It is absolutely maddening to do this part with quad inks. If I have 
to I'll just take a good guess with the quads in there, only did that 
once. It still seems to print okay if you're a bit off, I think. Also 
don't know what I'll do when I go CIS/CFS.

> >
> >  You
> > > have more experience than anyone in cleaning heads and printer.
> >
> > Yeah, unfortunately.<g>
> 
> You deserve a Purple Heart!
<G>
Jim H.
> 
> Martin
>