[pure-silver] Re: RE3200 SHEET FILM? was Re: Ilford developers
- From: "Richard Knoppow" <dickburk@xxxxxxxxxxxxx>
- To: <pure-silver@xxxxxxxxxxxxx>
- Date: Thu, 13 Sep 2007 17:02:28 -0700
----- Original Message -----
From: "Shannon Stoney" <shannonstoney@xxxxxxxxxxxxxxx>
To: <pure-silver@xxxxxxxxxxxxx>
Sent: Thursday, September 13, 2007 7:06 AM
Subject: [pure-silver] Re: RE3200 SHEET FILM? was Re: Ilford
developers
Maybe you could use an 8x10 hand held.
My tests of Delta 3200 show that for me, in DDX, its real
speed is about ISO 600. Whenever I've tried shooting it
at faster speeds, the film was underexposed. I like to
use it in the HOlga sometimes, since film speed is the
only control you have (there's only one aperture and
shutter speed).
I'm happy with slow films really for view cameras. It's
the hassie (and holga) that needs fast film, since it has
to be shot (hand held) at 1/125 of a second, at least for
me. I don't like the way a flash makes things look, and
it scares people.
--shannon
If measured using the ISO standard films like Delta 3200
and Kodak T-Max P3200 are around EI-800 but the films are
not processed to the contrast value specified in the
standard. The films are designed to be push processed as is
implied by the P in P3200. Any film can be pushed but
pushing does not really increase sensitivity. Rather, it
incereases the contrast. Since underexposing the film puts
most of the desired image into the curve region known as the
toe it is of very low contrast. The idea of pushing is to
raise the toe contrast to a value that's more easily
printed. Of course, the normaly used "straight line" portion
of the curve becomes very contrasty. The pushable 3200 speed
films have curve shapes that adapt them to push processing
by providing a somewhat longer range of toe exposure so that
pushing will not so often result in very difficult to print
negatives with extremely high contrast in those parts
receiving more normal exposure.
One must always distinguish between the ISO speed and the
_effective_ speed of a film. The ISO standard which applies
to B&W silver image film for still cameras has a specific
range of densities which will result from a specified range
of exposure and development. Effectively, the gamma or
contrast of the film is specified. If the film is exposed
and developed to another value of contrast the ISO speed is
no longer valid. The nature of the film is such that nearly
all films will loose about one stop when exposed and
developed for about one paper grade less contrast than given
by the ISO test and will gain about one stop when exposed
and developed for about one paper grade more contrast. The
change in exposure controls the maximum density values,
change in development changes the slope of the contrast
curve. Of course they are interacting.
Different standards apply to other types of films:
there are standards for motion picture B&W films and special
purpose films (like aerial film) and a whole different set
for color films.
AFAIK, Kodak and Ilford do not make their extra fast
films in sheet form because they are too sensitive to
fogging agents and possibly radiation. Kodak puts up P3200
only in 35mm cassettes, which is about the most protected
form of film. Ilford also puts up their film in 120 rolls,
which also have a reasonable amount of protection. Film of
any sort is considered a perishable, like fresh fruit or
vegetables and like them some is shorter lived than others.
No manufacturer wants to put up a product which will spoil
in storage and have to be tossed out.
---
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx
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