[Alt-photo] suggestions about cyanotype curve

Christian Nze christnze at gmail.com
Thu May 25 17:13:54 UTC 2017


Less ink

Le 22 mai 2017 20:50, "Don via Alt-photo-process-list" <
alt-photo-process-list at lists.altphotolist.org> a écrit :
>
> Sounds like you have too much UV blocking with your digital negative.
>
> Have you printed a regular analog step tablet to determine the contrast
> range of your process?
>
> Just a thought.
>
> Don Bryant
>
> -----Original Message-----
> From: Alt-photo-process-list
> [mailto:alt-photo-process-list-bounces at lists.altphotolist.org] On Behalf
Of
> Bob Cornelis via Alt-photo-process-list
> Sent: Monday, May 22, 2017 1:25 PM
> To: alt-photo-process-list at lists.altphotolist.org
> Cc: Bob Cornelis
> Subject: Re: [Alt-photo] suggestions about cyanotype curve
>
> 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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