Digital BW, The Print

Martin, Todd, Paul, everyone,

You all bring up extremely good points. I am going to limit myself to 
two observations and one experiment. I'm doing this because something 
CHANGED on my system and I need to isolate it. This change in workflow 
or settings turned a great print done in Febuary, which I have in a 
light tight box as reference, to a trashy posterized print done two 
days ago. However imperfect or perfect my workflow/ print file/combing 
was in Febuauary, it got worse from the same exact file and same 
settings in June.

I use an 1280 with standard VM inkset, which I (perhaps 
uneconomically) use virgin vacuum filled carts with. I bought my first 
six bottles of ink in January, my second arrived April 9th. So one 
change that happened was I started filling from a new set of bottles. 
I swab tested them to be sure they were not mislabeled and I double 
checked labels as I filled carts.

The second change was that I loaded Photoshop 7 on my system (Win98SE) 
on April 22.

The things that changed are: time, inkset bottles (same batch?), and 
pshop 6---->7.

If the ink gooped up my printer over "time", I may see it get better 
in both ps6 and 7 after running Epson carts in it for a couple of 
days. I suspect this is not the case. Since no CIS is involved we can 
rule out all the little problems it can cause.

If the two sets of inksets differ, MIS would have long heard of it by 
now from many other folks. I think this can be ruled out, escpecially 
since they were bought only 3 months apart.

If when I put a new set of carts in after the OEM ink run, I can, from 
the same file, duplicate the good print using PS 6 and duplicate the 
bad print using PS7, then the variable that messed up the print is the 
conversion algorithim in PS6 vs 7. If the result from this experiment 
is positive, it locks out the other two variables and a lot of other 
things as the culprit. And someone then has to discover what changed 
in PS7.

Oh well. All speculation until I run those two prints- maybe Thursday, 
Friday.
 
The second note is that I tried Culbertson's technique, suggested by 
Martin, to convert from greyscale to RGB and then apply one of Paul's 
curves in both PS6 and PS7. What's very interesting is that using 
Culbertson's method, PS6 and PS7 give identical mean, SD, and median 
values for my test print using the VM workflow, down to applying 
Paul's curve. BUT, the values in the histogram differ from both PS 6 
and PS7 when the regular greyscale gamma 2.2 convert to sRGB is used 
(Paul's workflow). And of course as already stated way back in a 
previous post, the values differ between PS6 and PS7 using the gamma 
2.2 greyscale--->sRGB.

 So one gets three slightly different files going to the printer 
depending on whether you use grey gamma 2.2 to sRGB PS 6, grey gamma 
2.2 to sRGB PS7, or Culbertson's channel conversion to RGB method 
(PS6/PS7 independent).

What is puzzling to me is Martin not getting quite as large a 
difference as I did when he tried the gamma conversion in both ver 6 
and ver 7. It could still be that I'm overlooking some setting, but I 
really can't think of what it is. Maybe it just depends on which file 
one uses(?), not just how dark or light it is?
Jim H. 






--- In DigitalBlackandWhiteThePrint@y..., "Martin Wesley" 
<mwesley250@e...> wrote:
> Todd,
> 
> We have discussed all of your points at one time or another and I 
believe we
> are pretty much in complete agreement. Posterization can have many 
sources.
> The most common is probably over manipulating 8-bit files and I 
think the
> second maybe scanning.
> 
<snip>
> 
> I can see what is happening to the image data with this workflow. I 
have no
> idea what is happening to the data with the Piezo driver or a RIP. 
<snip>

> 
> I think bottom line some images don't work. They don't work in 
silver
> either. Sometimes a neg is just too flat in some areas to be 
useable.
> Sometime a digital approach will pull it out but not always. The key 
may be
> to have a variety of drivers and ink sets available just as you had 
a
> variety of papers, developers and toners in the darkroom. I have a 
second
> 1280 that I have been using to try different ink sets. I would like 
to leave
> that set up with PiezoTone and keep VM in the other (I am 
considering
> switching to the Sepia-VM though). I need to set up a third 1280 
then for on
> going trials but I am out of room. Adding a RIP for the VM and 
PiezoTones
> would further increase options.
> 
> I think the multi-printer, ink set, driver approach is the way to go 
rather
> than trying to find the one perfect system. Different images are 
going to do
> better on one than the other. I generally like the Epson driver for 
sky and
> clouds, and the Piezo driver for images with lots of fine detail for
> instance. I think your remarks on the different ink sets have 
different
> transition points is valid and supports this idea.
> 
<snip>