Flash with pinholes

Hi everyone,

Quite a while back, someone posted some data about
pinhole exposures using multiple flash firings. I
can't seem to find it. Does anyone have a copy of this
they could send me or post? I've been photographing
for decades, but almost never use flash and it always
confuses me. I'm thinking that, assuming an f number
of about 250 for the pinhole, if the scene meters at
say 8 seconds at f=22 (which is typical of the studio
nudes I do) then the pinhole exposure would be in the
neighborhood of 30 minutes, which works, I know from
experience (although that can be tripled--which is
very hard on a model!).

Using flash at about 1.5m from the subject, how many
times would I need to fire the flash to expose skin
tones at a reasonable value? I'm guessing that f=5.6
at 1/60th of a second is about right for an actual
flash exposure with a lens. That suggests that, at
f=250, I'd need to increase the exposure about 10
times. Does ten flashes sound about right? Anyone have
any ideas about this? Has anyone come up with a useful
rule of thumb--a way of converting a metered exposure
to a series of flashes with a pinhole? I use a Pentax
spot meter.

Also, how does reciprocity come into this, I wonder?
If the actual exposure would be only the duration of
ten flash firings (only about 1/6 of a second, if each
flash lasts 1/60th of a second--which it may not, I
have no idea), then maybe there is no reciprocity
issue at all, even though the "underlying" non-flash
exposure would be quite long. Hmmmm.....

Thanks

Colin
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Received on Thu Feb 3 09:40:31 2005