Re: studio photography / flash

To change from f22 to f32 you must increase your exposure by 2 times, from 32
to 45 another increase of 2 times, 45 to 64, another 2 x, 64 to 90, another 2
x, 90 to 128, another 2 x, 128 to 180, another 2 x. This is the same as
multiplying your exposure like this, 2x2x2x2x2x2=64. Each stop requires a
doubling of the exposure. A 6 stop increase is 64 times the exposure. You can
think about it as your extended exposure time in sunlight. A one second
exposure at f22 would be equivalent to a 64 second exposure. Doubling 1 second
makes 2 then onward to 4, 8, 16, 32 and finally to 64 seconds. Since your flash
is an instant burst of light you need to pop it off multiple times to make the
exposure correct. If you did it 6 times it would be like giving it 2.5 stops
more light.

DAlfrey@aol.com wrote:

> In a message dated 11/20/00 11:59:18 AM Central Standard Time,
> peregoy@gl.umbc.edu writes:
>
> << Do you have a flash meter? If you do then you can determine the exposure
> time for your pinhole lens by metering your setup then decide how many
> stops different your pinhole is from your reading. For each stop off you
> will need to double your exposure.
>
> Say your meter says to use f 22 but your pinhole is an f 180, this is a
> 6 stop difference. to get the right exposure you would need to set your
> flash off 64 times.>>
>
> I too, would be interested in hearing about this , as I too, have a Santa
> Barbara pinhole , and studio flash unit... 64 times of popping the flash? is
> that a typo, ? I can believe 6 times, to compensate for the f/stop
> differential and the reciprocity , but 64 ?....... Santa Barbara gives a
> working f/stop of F/177 on their data sheets .
>
> _______________________________________________
> Pinhole-Discussion mailing list
> Pinhole-Discussion@pinhole.com
> unsubscribe or change your account at
> http://www.pinhole.com/discussion/

--
Chris Peregoy | http://www.gl.umbc.edu/~peregoy | http://imda.umbc.edu/