3880 calibration

3800
3880
piezography

#1

Hi all,

I’m fighting with some banding I get in the digital negatives I make with a 3880. Something no one could notice in a normal positive print.
The printer is relatively new to me, and I’m playing with the platen gap and feed A settings.
It seems the better results - actually good - are reached with a + 0.70% “paper feed adjust A” setting, which is the maximum.

  • Does that sound like something is not right with the printer?

Walker recently drew my attention to “CR and PF head-slant calibrations”.

  • could it be my 3880 needs calibration?

  • That should be done by some expert, right?

  • should the printer absolutely be plugged into an UPS to reach maximum precision?

Thanks for your help.

Stefan


#2

I’ve been trying different ink limits too, with some results.
Four channels of my 3880 are dedicated to making a type of negatives I need. They all run with black Inkthrift CL and follow the same curve.
Yes, I get enough Dmax for my use.
It seems that having the four channels firing with the same ink limit is not desirable, and also that going above a certain amount of ink leads to micro banding, though the OHP could take much more.

I wonder about a possible moire effect, but was told on the QTR forum that this should not happen because every channel has its own algorithm.
Still, I believe algorithms don’t mean stochastic and that moire is possible.

Please, could someone explain me if and why there is something wrong with using the same ink shade in four - or more - ink positions, following the same curve, with the same or different ink limits, in terms of banding, artefacts, moire, graininess, etc…?

Thanks

Stefan


#3

Stefan. Are you using PiezoDN? If so, there’s lot of support at the private forum for that: piezodn.inkjetmall.com

Three inkthiftCL black inks are going to cause grain and lines.

-Walker


#4

Thanks Walker,

I’m carbon printing, and PiezoDN is not set yet for carbon.
I red so much about clogs and had my share, I’m very afraid of pigment inks. ITCL gives me the densities I need… Actually, a 50% dilution does.
And peace of mind… in this regard.

I understand the different shades, partitions, curves overlapping, etc… to print positives. Piezography is great.
When it comes to negatives, difficulties start where only the darkest shades are used anyway (no grain or lines in the 20%-100% of my carbon prints).
Let’s takes the 5% patch of a step tablet. 95% in the negative. How many inks is PiezoDN using here and what shades? Why couldn’t the entire negative be printed with those inks?
Unless you want a printer that allows regular Piezography too, I don’t see the point of using light shades, fired massively, to produce the dark tones of the final print. You will never see any artefact there anyway. Well I don’t.

So three ITCL black inks will print grain and lines, and I’m fighting with four…
I wish to understand why the addition of each three/four channels, printing smoothly individually, will print lines.

Is it because inkjet is not stochastic?
Are there channels that should not be used simultaneously (e.g., MK and LLK are not designed by Epson to print simultaneously with the same ink limit, except probably at one crossing point)?
Does it have to do with the lack of “laser-precision” of the machine?
Are there maths involved here?
Is the ink composition involved?

Stefan


#5

You need multiple (at least 4 or 5) channels to make a random enough dot to print negs without lines.

Secondly, you DO need lighter shades so the total ink limit (TIL) can remain just about the same from dark to light instead of decreasing from the mid-tones to the printed shadows. The less ink the more lines.

Thirdly, PiezoDN ink overlaps are not just about lines, they are also about making sure the neg has no grain. This may not be “see-able” when printing on rough paper without a vacuum table but we built a neg system that could do silver and have micro-details like a real negative.

best,
Walker


#6

OK, this kind of makes sense to me. My little experience shows there must be a balance to find where things match, and PiezoDN probably does that.

Something worries me: I just tested the printer, each channel one at a time, same ink, same ink limit, same printer settings.
Some channels actually don’t make the good job others do.
K is clean, C shows slight micro banding, etc…
I don’t see how the best negatives could be made with it.

Is a 3880 good enough to make negatives that can do silver?
Is it worth having it “calibrated” (CR and PF head-slant calibrations) by a specialist?
Should I really go for a 7900?

I’m throwing in the towel, and start to save some € for PiezoDN…

Many thanks,

Stefan