Digital BW, The Print

Alessandro,

You wrote:

>I suppose that MIS Full Spectrum quads densities are very similar - if not
>equal - to Piezo, given that these inks are also known as "Cone clone".
>Am I right?

They are very close, and they should be the same.  I'd assume they are a
feasible substitute with at most minor corrections.

To be honest, I haven't actually tried the production FS inks to see why
some users thing there needs to be a slight correction in the Piezo driver
dot gain (or whatever it is) box.  I'm wondering if MIS missed the densities
slightly.  Given all the density fluctuations with the Piezo and CIS
combination, it may be that some of that affected the design criteria, but
I'm guessing.  (I was not involved in finalizing the mixing ratios.) On the
other hand, what I've found with the MIS VM system is that some Piezo
customers got used to their malfunctioning Piezo/CIS systems and thought the
distorted g/s ramp was normal. So, they may be "correcting" the system to
replicate their mal-functioning Piezo/CIS systems.

Basically, though, the big picture is that the MIS VM, FS and Piezo inks are
about the same.  I'm trying to establish an open system with competing inks
and workflows so that no one company can get a monopoly and stick it to us.
B&W photo has always been a technology that is affordable and easy for
creative types to use and manipulate.  I want to be sure it stays that way.
So, if the FS densities aren't right on, I'll get some and see what can be
done to correct the situation.

I might add that I've detected density differences between batches of inks
from the same company (both Piezo and MIS). There is no such thing as total
accuracy here.

However, one reason we need the ink companies to do our basic ink mixing is
that my quick and dirty syringe mixing is not accurate enough to give
sufficient consistency.  One needs very accurate scales and large volumes to
be even close to consistent with some of these critical ratios -- I'm
talking three digits of accuracy.  The light inks are affected by changes in
their mixing ratios to the hundredths of a percent.

> I have a set on its way to my eager hands, and I was planning to
>measure densities as well, but if you already did it I'd definitely trust
>your results rather than mine.

Well, you really need to compare, for example, Piezo and the FS inks on the
same system with the exact same materials.  The density ratios I put out
there are what I get for my system.  All systems are a little different.
So, get the curve, 21-step test file, and print some Piezo (from a cart --
not an old CIS that may have affected densities) and see what densities you
come up with.  Then try the other ink and compare.  Expect + or - 1-2% just
from printer variances.  Even high end 7000s and drum scanners don't seem to
be more consistent.  Perfection is impossible here.

Paul
http://www.PaulRoark.com

___________________________________

Alessandro Pardi

-----Original Message-----
From: Paul Roark [mailto:paul.roark@...]
Sent: gioved\ufffd 1 novembre 2001 22.07
To: DigitalB&WPrint
Subject: [Digital BW] Quad Ink Densities



To judge ink densities, I print the 21-step test file using what I call my
"Color Test" curve.  (The driver settings I use for this include Matte HW
paper type and No Color Adjustment.) This basically pumps out 100% of each
ink at a different part of the test strip.  Then I scan the test strip and
do a levels on it.  So, black is 100% and white is 0% when measured with the
eyedropper in Photoshop (if the image is in grayscale mode).

Scanner settings, etc. can affect results, so I use the tool just to compare
inks -- and mix new brews.

Piezo gives results as follows: K = 100, C = 84, M = 38, Y = 27%.

<huge snip>