But then you would have the *actual* guide number instead of the
marketing guide number. I've never yet measured a flash that isn't at
least 1/3 stop (and often 1/2 to 2/3 stop) less than the claimed guide
number and with very significant fall-off at the edges of the supposed
field coverage. Factory guide numbers have a lot of assumptions behind
them such as distance to surrounding walls and ceilings and reflectivity
of same which all feed back more light by reflection with the effect of
raising the guide number. Shooting in a big, dark paneled restaurant or
dance hall invalidates the guide number from the very beginning even if
it was reasonably accurate (to its unwritten assumptions) to begin with.
As I said, turn it to manual, guess at the aperture, fire the flash,
chimp and adjust the aperture if required. 1 or 2 test shots will
usually suffice with a small amount of practice. You should also be
able (I think) to get rid of the onerous pre-flash nonsense. Or, as AG
suggests (tongue in cheek), actual measurement with a meter ain't bad
either except that it's difficult to do without a cooperating assistant.
Dr. Flash
usher99@xxxxxxx wrote:
> ( Still can't find the GN/joules on the G11--someone
> should put it on full dump and measure it.)
>
> An embarassed student of Dr. Flash,
> Mike
--
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