Wrote Shawn:
>> I cannot at all agree with Shawn's statement that grain is determined
>> in manufacture. (that was me, Lars B)
>Actually, it wasn't me who said this, although I do tend to agree, at
>least in
>practical terms. Take a film like HP5+ compared to Pan F. PanF has a much
>thinner coating of silver, which in nearly all cases will result in a finer
>grain. Sure, you could probably get HP5+ to give as fine grain as PanF if
>exposed at EI 25 or 50, but why would you want to? And conversely, I have
>pushed PanF and seen it show nearly as much grain as HP5+, but with extreme
>contrast.
I stand corrected as to the author ... Now, faster film is coated thicker than
slow; you can see that fast film emulsions transmit less light. A thicker
coating will tend to increase the visible sensation of grain, as grains at
different levels can overlap. --Before coating, emulsions also undergo a
process called 'ripening', i.e. incubation on low heat. This makes the halide
crystals grow. With a larger gross section, there is more chance that a grain
will be hit by a photon, so the emulsion will be more sensitive. But larger
grains will also tend to receive more hits, and each hit produces an atom of
reduced silver, around which silver grain grows during development. So
obviously, development is not everything. You can make HP5+ grain finer,
but not as fine as a really slow film. But of course pushed PanF and 'pulled'
HP do overlap!
>But what you have done is started with an already fine grain (and high
>accutance) developer/film combo, and added a silver solvent to further soften
>the edges of the grain, similar to what Microdol-X and Perceptol will do,
>right?
In classical 'compensating fine grain'developers such as dear old D-76,
sulphite
has three roles, as a preservative (it is a standard industrial
anti-oxidant), as a
mild alkali and as a silver solvent. So adding it was certainly nothing
new. This
was what workers such as Dr Paul Wolff did in the 'thirties when they replaced
the old high-alkali developer formulas of the glass plate era with modern-style
recipes for 35 mm work.
And TMX does have fine grain--better at least than old PanF and Panatomic.
Still, grain becomes noticeable at enlargements above ca 7 x, at least if you
use a condenser enlarger (as we do in Europe) and focus it religiously on the
grain (as I do). Also, negative gradation is important. A long grayscale
with lots
of large middle tone areas, such as in landscapes---the sky, for
instance---does
make grain visible. I once photographed my black-and-white cat on a black-and-
white piece of fabric with Tri-X developed in D-76, enlarged him to 24x30 cms
(something like 10x12", or 9.4 x) and there was no visible grain at all!
Also, practical workers tend to confuse objective and subjective grain. When
they say that 'there is no grain in the print', they mean 'no grain above my
limit of acceptance', not 'no discernible grain'.
>I don't think anyone would claim that grain is written in stone by the
>manufacturer. Even comparing the results of Ilford's suggested film/dev
>combos
>with a particular film will reveal a wide range of grain sizes, and these are
>conservative combinations to say the least.
Right you are!
Vänliga hälsningar/Best regards
Lars Bergquist
Välkommen till/Welcome to ...
<http://www.bahnhof.se/~timberwolf/>
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