[pure-silver] Re: hp5+ at 125 development times
- From: "Richard Knoppow" <dickburk@xxxxxxxxxxxxx>
- To: <pure-silver@xxxxxxxxxxxxx>
- Date: Sat, 10 Oct 2009 14:25:57 -0700
----- Original Message -----
From: "photovergne" <wilbert@xxxxxxxxxxxxxxxxx>
To: <pure-silver@xxxxxxxxxxxxx>
Sent: Saturday, October 10, 2009 1:28 AM
Subject: [pure-silver] Re: hp5+ at 125 development times
Tim Daneliuk wrote:
Jean-David Beyer wrote:
Shannon Stoney wrote:
Hi, I accidentally shot some hp5+ at 125, because I
thought I had fp4+
in my camera.
By about what percentage should I reduce the development
times? I
normally develop it in DDX 1+4 for about 11 minutes. I
was thinking
maybe...9 minutes?
Don't shorten the development times because that gets
you lower contrast.
The real rating of HP5 is 200 ISO. So you only overexposed
2/3 of a stop. That's not a problem with normal
development and normal lighting. But to be sure you can
use Perceptol / Microdol X which lose you about one stop
of sensibility. So you end up with N development times and
even smaller grain.
Just my 2 cts.
Wilbert
http://phot-o-vergne.com
I am always curious where these "real" ratings come
from. In fact film speeds are determined by a well
controlled method detailed in an international standard. I
think, however, Ilford rates film at a lower contrast than
the one obtained by following the ISO standard so, if
measured by the exact ISO method the film speed should be
slightly higher than the box speed.
I have detailed the speed measurement method in detail
in this group several times, once quite recently, so will
not do it again here. _Effective_ film speed is dependant on
many factors such as the type of developer used and the
contrast index desired. Also, while its true that the ISO
speed is supposed to give the minimum exposure needed for
good shadow detail many photographers find that a somewhat
greater exposure give them better tone rendition. This may
well be due to exposure and processing conditions that do
not match those in the standard.
The fact is that nearly all pictorial B&W films have
enormous overexposure latitude, as much as twelve stops for
some film. That means the film can be overexposed by that
much and still give good tone rendition. Certainly a couple
of stops is well within tolerance for good tone rendition.
--
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx
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