[pure-silver] Re: Under exposed frame
- From: Ryuji Suzuki <rs@xxxxxxxxxxxxxxx>
- To: pure-silver@xxxxxxxxxxxxx, chris.woodhouse@xxxxxxxxxxxx
- Date: Wed, 05 Jan 2005 15:15:46 -0500 (EST)
From: Christopher Woodhouse <chris.woodhouse@xxxxxxxxxxxx>
Subject: [pure-silver] Re: Under exposed frame
Date: Wed, 05 Jan 2005 17:48:31 +0000
> Above the threshold, the halide system is continuous, irrespective
> of the emulsion combination.
The threshold effect must be considered at individual crystal level.
(Sensitometric curve analog I gave is a watered down version.)
In ordinary pictorial print emulsion and developers, individual grains
are either fully developable or not developable at all. There is very
little time in transition from the beginning of development to
completion for a single grain. The difference is whether the grain has
a development center or not. Enough number of high energy photons must
hit the crystals in order to make latent image of sufficient silver
cluster that can act as the development center. Those crystals that
are not developable after G2 exposure remain below the threshold.
There is some room for stable latent subimage that is not developable,
especially for print emulsions. Crystals with these remain
subthreshold but they need fewer photons on average (these are all
stochastic phenomena, because of quantum nature of photon and the
limited efficiency of photoelectrons making photolytic silver) to
become developable. After G2 exposure, the shadow areas have more of
these guys that can be made developable by very brief G5 exposure.
--
Ryuji Suzuki
"Keep a good head and always carry a light camera."
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