Archived posting to the Leica Users Group, 1997/08/11

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Subject: Which Standard Focal Lengths ?
From: ABreull@aol.com
Date: Mon, 11 Aug 1997 15:30:17 -0400 (EDT)

In einer eMail vom 11.08.1997  18:54:55, schreiben Sie:

>I always thought that the "normal" lens was one where the field of view
>most closely matched that of the human eye.  For the 35mm format I
>understood this to be a 35mm lens, for 4x5 a 6" lens.  The 50mm focal
>length  for the 35mm format is a slight telephoto.  My "normal / standard"
>lens is a 35mm f/2 Summicron.
>
>

If you take those standards, then you are almost true: the 50  mm covers the
angle of the human eye, while the 90 mm covers the perspective of the human
eye. So, which is your standard?

The optical standard for a "normal"  lens is given by the equation I sent
recently (in short: the standard normal lens agrees to the length of  the
diagonal of the negative format).

- -Alf