Quote Originally Posted by MattKing View Post
You use exposure factors this way with shutter speeds, not apertures.

If your shutter speed was 1 second, the new shutter speed would be 1 x 2.15 x 2.5= 5.375 seconds.

If you need to use them with apertures, you need to use the base 2 log of the factor instead.
Can you break that base 2 log thing down for a dummy?