Chris has enlightened me on how to think about motion picture pinhole
exposures:
On Mon, 20 Nov 2000, Chris Peregoy wrote:
> 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.
>
Using a Bolex motion picture camera, I typically establish my shutter
speed to be 1/65 sec. (shooting 24 frames per second with 135/360 shutter
angle). I read a light meter to get the f-stop I should use. So, suppose
I read the meter and it says to use f/11. Since the f-stop I am actually
using with my pinhole camera is (I think) about 1/120, I will need a lot
more light than 1/65 of a second. How much more light can be determined,
as Chris suggests, by doubling this shutter speed, 1/65, for every f-stop
between f/11 and f/120. When I do this doubling six times, I get just
under 1 second. Bravo.
Bernie
Received on Mon Nov 20 16:28:29 2000
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