[Alt-photo] suggestions about cyanotype curve

Bob Cornelis bob at colorfolio.com
Mon May 22 17:25:13 UTC 2017


Hi Peter

Thanks for the suggestion. I think, however, that my problem is not lack of
contrast but, rather, too much contrast, at least in the highlights. The
rest of the tonal range, all the way down to the shadows are behaving
properly.

Regards
Bob


On Mon, May 22, 2017 at 10:10 AM, Peter Friedrichsen via
Alt-photo-process-list <alt-photo-process-list at lists.altphotolist.org>
wrote:

> Bob,
> Without seeing your samples, I can suggest one possibility; a thick
> coating of the sensitizer. I have found that contrast increases, the more
> one applies to the paper. It may be due to the uv blocking effect such that
> the sensitizer that is bound to the paper never gets a chance of exposure
> in the shadow areas due to the filtering effect of the sensitizer sitting
> overtop. Whatever the reason, that is my observation. I know others will
>  suggest other possible causes.
>
> Peter Friedrichsen
>
> > On May 22, 2017, at 11:04 AM, Bob Cornelis via Alt-photo-process-list <
> alt-photo-process-list at lists.altphotolist.org> wrote:
> >
> > Hi All
> >
> > I'm looking for a little help finishing a custom curve I've made for Ware
> > cyanotype printing using Peter Mrhar's method from Easy Digital
> Negatives.
> >
> > I'm having problems getting a smooth gradient from steps 0-10. Pure white
> > is step 0, pure black step 100. My tones from steps 10-100 are pretty
> > linear, but within the highlights I've got about half the steps pure
> white
> > and then there is a steep jump to a value of close to 10. I'd like to
> find
> > a way to get a smooth gradient in this part of the tonal range.
> >
> > Without a curve, all steps from 0-14 are pure white so the curve has to
> do
> > a lot of work to introduce a gradient in a relatively small portion of
> the
> > curve range. I've tried tweaking with the curve in that range by hand but
> > without success.
> >
> > I was wondering if there are other tricks people know of to handle this
> > type of situation, either chemically, through exposure, development, etc.
> >
> > My first wash is in 3% citric acid for a couple of minutes, 20 sec in
> > peroxide solution, then about 25 min in water.
> >
> > I've attached 3 screenshots for anyone interested showing my pre-curve
> and
> > post-curve step wedges (100 steps), and the curve itself (note it is a
> > pre-inversion curve).
> >
> > Thanks!
> > Bob
> >
> >
> > --
> >
> > http://www.bobcornelis.com
> > _______________________________________________
> > Alt-photo-process-list | altphotolist.org
> _______________________________________________
> Alt-photo-process-list | altphotolist.org
>



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