>I'm sorry if this isn't OM-content. Does anybody know a web site that
>can help me experiment with pushing film ? I've only found one web site
>that had a table with development times, but nothing like 'general
>guidelines'. I'm using Illford HP5 and the table went up to 1600ASA.
>Now, what do I do if I want to push it to 6400 or higher ? I know the
>film won't be performing at its best then, but I just want to experiment
>a bit *grin*
>
>Peter.
I have done this quite a bit. The only way to get dependable results with
your camera, your metering techniques, your darkroom conditions etc.
is to make controlled experiments. Use a subject with a normal range of
contrast. Make a series of exposures from nominal (ASA/ISO on the box)
and one, two, three stops under. If you cannot reload your own cartridges,
open the camera in total darkness without rewinding, remove the cartridge
and cut the unwound film and load it into the tank. Then cut a new leader
from the end of the film in the cartridge. I advise you to start with the
data you have; in my experience, they will already be pretty optimistic.
Evaluate the negs by actually printing them. Remember that as you
increase development, medium tones and highlights get denser, but the
shadows do not, not to the same extent. So the contrast of the negative
increases. With very long development you get density in the shadows
(chemical fog) but not more detail. Shadow detail is the limiting factor,
so obviously, a flat subject can be photographed at a higher EI than one
with high contrast!
In many cases, the most practical method is not to over-develop (press)
the film but to use a chromium intensifier. This adds an equal amount of
density to all image details, meaning that while the shadows get perhaps
1--5 % more, thin shadow details may get 100--200, making them printable
(you cannot print all the negative shadow detail you see, if you want any
area of maximum density---real black---in the image). So this works just
the opposite of pressing, which adds more density to the highlights. Good
pro shops have the stuff (I think Tetenal still makes it).
Vänliga hälsningar/Best regards
Lars Bergquist
Välkommen till/Welcome to ...
<http://www.bahnhof.se/~timberwolf/>
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