[pure-silver] Development modifications for higher sharpness

I did a careful experiment with slow and fast roll films to see if there was
a practical difference in image sharpness between development methods by
changing variables to deliberately induce edge effects. The results first
surprised me and then I believe I found a clue- which I would love some
comments on.

The developer was D76. In one case, the film was Jobo processed, at 24C with
1+1 dilution. In the second case it was stand development, inverted gently
every 2 minutes, at 20C and at 1+3 dilution. The development times were
about 5x different.

The films were Acros 100 and Neopan 400, an example of a slow and fast film.
Before the sharpness test, each went through a calibration procedure to
ensure that a fixed contrast index for each film could be reproduced.

The results:
Two films of winter trees against a uniform sky were taken, taken with all
due and attention to lens quality and vibration.

Acros 100 - absolutely no difference. Indistinguishable negatives and prints
between the development schemes.

Neopan 400 - Completely different. As the branches get thinner towards their
ends, they become darker and more distinct in the dilute developer. Grain is
slightly more apparent at 1+3 and the sky is slightly darker. This is with
identical print exposures. The slow dilute development gives high apparent
sharpness, especially in areas of high subject contrast.

Now the interesting bit. Going back to the film characteristic curves, I
noticed that the Acros 100 curve shapes do not change between the two
development schemes. The 'curve' in each case, is a perfect straight line
with no shoulder. The Neopan 400 on the other hand shows distinct signs of
highlight compensation in the more dilute developer.

Would it be fair to say that the two go hand in hand? That is, you cannot
get higher sharpness if you cannot induce highlight compensation?...or put
the other way around, you need a development scheme that has the developer
weakening in highlight areas, so that it can produce edge effects at a micro
level. For the same reason, the degree of development in large highlight
areas must reduce too at the macro level?
 
-- 
Regards Chris Woodhouse ARPS



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