From: Clay Harmon (wcharmon@wt.net)
Date: 07/17/02-05:55:43 AM Z
Shannon:
Hp-5 is notorious for reaching so-called 'gamma infinity' quickly. That is
where at some point, additional development does not increase the contrast,
but only adds additional base+fog density (not desirable!) . You may need to
use a staining developer such as PMK, rollo pyro or Pyrocat-HD, which will
give a proportional (to silver density) UV blocking stain in the highlights
and behaves like additional density when printing UV sensitive processes.
I use HP-5 with pyrocat-HD all the time in my big cameras and it works fine
with a density range of about 1.3-1.4. The stain actually makes the
effective density range more like 1.8-1.9. Pyrocat times for the density
range you're looking for would be about 11-13 minutes at 75 degrees. Check
out the Sandy King article at www.unblinkingeye.com for all the info. It
also is one of the cheapest developers around, and is pretty easy to mix.
Staining developers are about the only way to go with HP-5 for alt-photo
density ranges, unless you only shoot really high contrast scenes. The
pinhole may be making your efforts a little harder also because of internal
flare.
Clay
on 7/17/02 12:48 AM, Shannon Stoney at shannonstoney@earthlink.net wrote:
> I am shooting HP5+ in the 8x10 format in a pinhole camera for cyanotypes. I
> am having trouble getting the highlights dense enough. I am up to a 20
> minute development time now, and still the highlights only have a density of
> 1.71. I would like a density range of about 1.6, starting at 0.35, say, in
> the shadows. (I have to shoot it at like 3200 to get the shadows this
> thin!) Should I keep increasing the development times? Is it "bad" to go
> over 20 minutes? I process in straight D-76 in a homemade BTZS-style tube,
> at 68 degrees. I am thinking maybe I should make the temperature warmer
> rather than making the times longer. But, then what will I do if I ever
> have to increase the development time further for a low-constrast scene?
> (Excuse the cross posting if you read
> the pinhole and alt-process lists.)
>
> --shannon
>
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