John,
Thanks for a really interesting talk. I thought the whole hardware and
software limitations were really interesting to hear about!
Cheers,
--Christer
On Fri, Jun 20, 2008 at 11:10 AM, John McKelvey <[EMAIL PROTECTED]> wrote:
> Thanks for so many being there, and all most all staying awake.. {:-)
>
> I forgot in the photography portion to bring up something I found
> interesting when I read about it in the late 1970's. I pointed out last
> night that it took about 5 photons, presumably reflected through the lense
> from the photo subject of interest, to render a silver halide grain
> developable ...
>
> Now think solid state devices and "gating." Suppose it takes 5 volts to
> cause a device to "go on." If a constant bias voltage of 2.5 is always
> there then it only takes an additional 2.5 volts to trigger the device.
>
> Now back to film: suppose that the film plane is flodded with 2.5 photons
> just before exposure by small LED's in the camera. Then it would only take
> 2.5 photons of light through the lens to generate a developable grain. This
> would mean doubling the effective film speed without increasing the grain
> (typically related to film speed.) In the late 1970s the idea was
> successfully tested, and it succeeded. Exposure requirements were reduced
> by almost a factor of 3 if I recall correctly.. an increase of effective
> "system speed" of 3, or 3*400 = 1200 effective speed for TRI-X.
>
> Cheers, and thanks for letting me talk.
>
> John
>
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