Tom Scales wrote:
> I'm confused. I thought one stop was the square root of 2 brighter (about
> 1.4) and TWO stops was twice as bright.
>
> Am I missing something?
You just have it backwards.
One Stop is twice as bright. To double the area of a circle you multiply
the diameter by the square root of two. The increase in brightness is a
power of two. A two f-stop increase is 4 times the light (2*2). A three
f-stop increase is 8 (2*2*2) times the light, etc... To achieve a one
f-stop difference with a starting aperture of 1.0 the diameter needs to be
multiplied by 1.4 (the square root of two). To achieve the f-stop you
divide the diameter of the diaphragm by the focal length.
Clear as mud now?
--
Mark Thalman, markt@xxxxxxxxxxxx
f u cn rd ths thn u cn gt gd jb prgrmmng cmptrs
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