From: Judy Seigel (jseigel@panix.com)
Date: 09/21/02-09:32:22 PM Z
On Sat, 21 Sep 2002 Ender100@aol.com wrote:
> I think the only readings you really need to take are reflective readings on
> the final print of your steptablet using whatever process (gum, platinum,
> etc) that you are using.
Frankly, I can't figure how I'd do that for gum -- because there is no
absolute: not like I had, say, a platinum emulsion, and did a curve to
make it behave. A reflective reading from a gum step tablet would only be
for that particular amount of pigment, color, ratio of dichromate to gum,
& length & type of soak... but these tend to vary by layer, paper, whim,
image, and available temperature.
I'd like a curve that would just print, say 8 differentiated steps. I
could get the 5 or 6 steps that's the average for average gum emulsion &
development, with range left over to fill in with subsequent colors.
Any ideas what could do that, or is that the part I've got to figure out
myself?
Meanwhile, I DID get Dan's curves on the desktop by pressing option key --
hoo ha !-- with many thanks to digital mavens in this crew. But Dan --
where was the "gum curve"? I opened every one that looked possible, but
the only one that seemed at all possible was the cyanotype curve, which I
loaded & will try.
Interestingly, it was somewhat like the curve on all my 4 tests so far.
It turned out (which is why actually charting curves is such a revelation,
at least around here) that even though the NUMBERS of the high part looked
very different for each material, the rest of the curve was quite similar.
The section with the first 5 (densest) steps ranged from very steep to
practically vertical, but after that the 4 materials were just about
parallel to each other and virtually flat.
Very curious.
TBC. thanks again so far.
Judy
Thus, as you said, you end up with just one
> adjustment curve. While curves are less destructive to data than the LEVELS
> command, I would hesitate to do them more than once for the final ALT-Curve.
> By doing it this way, you are at once linearizing the ink output of your
> printer, and adjusting for the alt process you are using, and the mix you are
> using and the paper you are using and the undershorts you are wearing. Just
> as long as you keep everything constant, including wearing your undershorts
> backwards and your printer driver settings and film etc etc, when your print
> your negative. I like to include my little step wedge with my print negative
> as a test to make sure I don't have some weird anomaly with a given negative
> and printing session. Otherwise you are likely to become victim of the evil
> Step Wedgie.
>
> I also think that doing a test strip with a Stouffer's first helps you figure
> out your approximate exposure value and the number of "Stouffer steps" that
> you hope your combination will render.
>
> Given that, you can then print your digital step-tablet and read the printed
> steps and calculate what your adjustments should be on your curve. Excel
> spreadsheets are great for this. I believe Dan suggested the trick of using
> the Transfer function in the printer dialogue box to enter actual %'s and
> then save the curve. It's a timesaver.
>
> Good luck with it!
>
> Mark Nelson
>
>
> In a message dated 9/21/02 12:22:31 AM, jseigel@panix.com writes:
>
> <<
> On Fri, 20 Sep 2002 Ender100@aol.com wrote:
> > If you made a step tablet on an imagesetter, you would get more density, and
> > thus the capability of steps more similar to a Stouffer's. Digital film
> from
> > an imagesetter will render density between 3.0 and 4.0 I believe.
> >
>
> Hi Mark,
>
> My theory so far is that I should have the step tablet on the material I'm
> going to be printing the negs in, otherwise I might as well use the
> Stouffer. I realize my reasoning has been amply flawed so far, and may be
> flawed in this -- If so, can you clarify?
>
> > As far as doing a steptablet by using the posterize command goes, it's
> > probably fine for gum. (hehehehe just kidding)
>
> That's OK -- there really is a tremendous amount of latitude in gum, or
> there is the way I print it, so maybe it is OK. On the other hand, if you
> need one kind of curve to get the steps even, and apply that to the step
> tablet, you probably need a DIFFERENT curve to make the image itself right
> for gum. But wouldn't I have to apply that curve to the step tablet on top
> of the other one, otherwise it would be irrelevant for that negative...??
> Begins to seem like 3-dimensional chess.
>
> > ....It will get you pretty
> > close, thought the steps may not be equal in size (if that bothers you).
>
> It makes me nervous to see giant steps in the highlights, just where
> you need slooooow... I don't care so much if they're even, as if they're
> small.
>
> Anyway back to the drawing board. thanks,
> >>
>
>
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