From: Judy Seigel (jseigel@panix.com)
Date: 10/30/02-01:10:46 PM Z
On Wed, 30 Oct 2002, Shannon Stoney wrote:
> It's kinda hard to make full use of the stouffer tab without a
> densitometer. I use the tab to figure out what the highlight density
> needs to be, and the densitometer to find out if it is.
I'm not sure why densitometer. In fact I did cyano, VDB, gum at al with
undergrads with step tablets for years without it... use the two white
cards with holes in them on the light box to match neg density to step
tablet density & no need of densitometer. In fact densitometer just adds
another step -- you've got to translate the log density back to the step
number. So it gives you an absolute number -- of no practical use.
I'll add, however, that it was a big help (tho NOT necessary) that we made
the negatives with step tablet in hand. That is, working backwards.
Print a step tablet on the target paper, see what numbers make good top
highlight and good d-max and make negs to match.
I haven't seen the reference cited above, but it sounds overly
complicated. Anyway, you might start by getting it "good enough" and
getting the feel for the process without angst. Then worry about perfect
next week.
cheers,
Judy
> Surprisingly, for normal cyanotypes (the classic formula), the
> negative does not have to be much denser than a normal silver
> negative! My negatives processed for silver work fine, if I process
> in plain water, and if I use Crane's platinotype paper.
>
> However, I like a longer scale, so I process in a dilute solution of
> water and vinegar, 5:1. This is the first bath only, for one minute;
> after that, plain water for nine minutes. That way, I get a longer
> scale. And, I have to make a negative that fits this, so I
> discovered from the step tab that I have to get the highlights up to
> about 1.9. You can find this out quickly with a densitometer, but if
> you don't have one, just keep increasing your development time until
> the highlights print the way you want them to.
>
> The other great use of the stouffer tab is to figure out whether the
> print is "done" or not in the sun. The exposure times will vary from
> day to day and month to month, unlike with a UV unit. I check from
> time to time, and when step #6 is darker than both five and seven,
> it's ready. This may seem strange, but you'll see what I mean if
> you try it. It has to do with the self-masking thing I think.
> Anyway, the lower steps get darker and darker and then they begin to
> reverse. When 1-5 has reversed but six hasn't, it's done. At least
> that's my test. Of course, this is only for negatives that have a
> perfect density of about 0.35 in the shadows to 1.9 in the
> highlights. Negatives with overexposed shadows might have to be
> printed until step 7 or 8 is the lowest unreversed step. Again,
> you'll see what I mean if you try this.
>
> It really is helpful to have a densitometer, but it's definitely
> possible to make good cyanotypes without one.
>
> A helpful book on getting everything calibrated without using a
> densitometer--ie your shadows and highlights, and exposure and
> development--is The Practical Zone System by Chris Johnson. If you
> go through his simple process, your negatives will start matching
> your cyanotype emulsion better. Then you can use this same testing
> process when you do albumen, or any other process.
>
> --shannon
>
>
>
>
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