Archived posting to the Leica Users Group, 1998/05/01

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Subject: Re: [Leica] Leica lenses stopped down below 5.6
From: Eric Welch <ewelch@ponyexpress.net>
Date: Sat, 02 May 1998 00:23:50 -0500

At 06:52 PM 5/1/98 -0400, you wrote:

>passing the edge of the diaphragm increase. The conjoint effect of both
>factors results in maximum sharpness when the lens is stopped down two or
>three stops from maximum aperture. For an F2.0 lens, this would be about
F4.0.

That depends on the lens. The Leica 280 f/4 apo telyt is at optimum
aperture wide open. It's diffraction limited, according to Leica. The 180
2.8 Elmarit (second version) is optimum at f/4. Each lens is unique in it's
characteristics. No rule of thum can cover all lenses. Leica lenses seem to
need less stopping down than most other lenses in my experience.
==========

Eric Welch
St. Joseph, MO
http://www.ponyexpress.net/~ewelch

Maintenance-free: When it breaks, it can't be fixed