Archived posting to the Leica Users Group, 1997/02/18

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Subject: Re: Pinhole f number
From: "Juan F. Sanz Cervera" <Juan.F.Sanz@uv.es>
Date: Tue, 18 Feb 1997 13:51:30 +0100
 
>From: photology@juno.com (Thomas P Myro)
[...]
>
>The numerical aperture of any lens is calculated by dividing the focal
>length of the lens by the RADIUS of the physical aperture--1/2 the
>diameter of the hole, in mm. in regards to the pinholes.

I may be wrong, but I always thought that you have to divide the diameter of
the aperture (or the diameter of the hole, in the case of a pinhole) by the
focal length.

Regards,

     - Juan