[pure-silver] Re: Under exposed frame
- From: DarkroomMagic <info@xxxxxxxxxxxxxxxx>
- To: PureSilverNew <pure-silver@xxxxxxxxxxxxx>
- Date: Thu, 06 Jan 2005 01:24:01 +0100
We need conduct the test, and see if the theoretical effect is measurable
and meaningful to practical photography.
Chris Woodhouse has the best equipment and the needed experience to do this.
I will hold my final judgment until I see his results.
Regards
Ralph W. Lambrecht
On 1/5/05 9:15 PM, "Ryuji Suzuki" <rs@xxxxxxxxxxxxxxx> wrote:
> 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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