Archived posting to the Leica Users Group, 2003/07/29

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Subject: Re: [Leica] arggghhh... rant at Keeble & Shucat...
From: Eric Welch <eric@jphotog.com>
Date: Tue, 29 Jul 2003 23:12:02 -0700

A common mistaken notion. Focal length does determine focusing accuracy 
with rangefinders. As the focal length increases, accuracy drops. And 
at about 75 mm, the rangefinder becomes about as accurate as focusing 
with an SLR. The wider the focal length, the more accurate a 
rangefinder is compared to an SLR.

This is a well-known phenomena. And it has to do with the angle of view 
of the rangefinder and how wide the rangefinder base is. So a camera 
with a narrower rangefinder base (the distance of the rangefinder 
window from the viewfinder) is going to be less accurate than one with 
a wider base. So, the Leica CL is less accurate than the Leica M 
because the rangefinder base is narrower. This principle actually works 
with SLRs too, where the effective rangefinder base is the physical 
width of the lens elements of the lens determines its focusing "base."

On Tuesday, July 29, 2003, at 09:02  PM, Mike Quinn wrote:

> Focus accuracy in the M series has little, if anything, to do with the 
> focal
> length of the lens. You can get more depth of field with a higher 
> f-stop.

Eric Welch
Carlsbad, CA
http://www.jphotog.com

If you find yourself in a hole, stop digging. - Will Rogers.

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Replies: Reply from Karen Nakamura <mail@gpsy.com> (Re: [Leica] arggghhh... rant at Keeble & Shucat...)