Re: [APML] Pre-Flashing Slide Film

[Chuck Vaughn <aa6g@aa6g.org>]

I wanted to make a few observations about pre-flashing and I'm not
tying to discourage those of you experimenting with it although
it'll sound like it.<g>

Pre-flashing has been known for a long time but was basically given
up on when gas hypering came along, in part because it is more difficult
to do correctly than gas hypering. If I remember correctly, it also didn't
show any particular advantage over gas hypering. If pre-flashing had a
real advantage over gas hypering we'd all have setups to efficiently
pre-flash our film. Lumicon would be selling preflash equipment instead
of hypering tanks.

Also a slow form of pre-flashing occurs during the exposure in the form 
of sky fog. A little sky fog can actually help, especially if the film
is a bit underhypered or the exposure is less than the sky fog limit.
I found this out in my manually guided C14 days when I could only expose
for 1 hour maximum. Photos at a light polluted site recorded more in the
same time than those from 10,000 feet in the Sierra Nevada. The latter
didn't receive the benefit of sky fog pre-flashing the film.

Chuck <aa6g@aa6g.org>

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