SNIP-
>Linear interpolation is a good approximation for small differences,
>but since the progression is _geometric_[1], not linear, the
>exact difference in stops between two f-numbers F1 and F2 [1]can be
>given by
>
> log ( f1 / f2 )
> ---------------
> log ( sqrt(2) )
>
>(where f1 is the larger of the two numbers).
>
>So for example f/1.8 is 0.304 of a stop wider than f/2
> f/1.2 is 0.445 of a stop wider than f/1.4
> f/1.8 is 0.725 of a stop more than f/1.4
>
>Enjoy,
> Chris.
>
>
>[1] Each f-number is the previous number multiplied by the square root
> of two. Approx 1.414214
>[2] Where F1 is the larger of the two numbers
>
>
Thanks, Chris. This non-linear explanation, semi-learned, but forgotten,
was what I was looking for.
Thanks to you all who gave such enlightening answers to my question. It is
appreciated.
God, this list is great!
Winsor
Winsor Crosby
Long Beach, California
mailto:wincros@xxxxxxxxxxx
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