Hi Tom,

Saying what the other posters have said in other terms, if you open up a
lens from say f/2.8 to f/2, you are increasing the radius of the
aperture circle by a ratio of 1.414, thus doubling the square area of
the aperture circle, thus allowing twice as much light to pass through
in a given amount of time.


Francis A. Miniter


Tom Gardner wrote:

Is there an easy formula to translate f-stops to the percentage of light
transmission? As each stop is 50% of the previous stop, where did the
numbers come from?