Archived posting to the Leica Users Group, 1999/09/15

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Subject: Re: [Leica] ....M vs R's...
From: Eric Welch <ewelch@ponyexpress.net>
Date: Wed, 15 Sep 1999 10:35:06 -0500

At 02:42 PM 9/15/99 +0800, claire wrote:
>The replies to this thread so far have this in common - ie, the M is
>unbeatable when it comes to focussing at low lite levels....  sorry... but
>why is this so ?

The mechanical rangefinder has a base much wider than the equivalent in an 
SLR with wide angle lenses. I'm not talking about a split image rangefinder 
in an SLR, but the way a focusing system works in an SLR. The apparent 
"base" is determined by several factors. The rangefinder base on a Leica M 
camera is much wider than an SLR's. The wider, the more accurate for focusing.

As focal length increases, this difference diminishes, and at about 
75-90mm, the SLR gets the advantage and thus for telephotos becomes the 
more accurate way to focus.

It's independent of eyesight, except that with a Leica M and wide angle 
lenses, you are looking through a bright finder rather than the lens to 
see. It's much easier for the eye to see the double image line up than to 
observe the focus on a groundglass with the subject so "apparently small."

>Also, "best suited to wide angle pics..." - does this mean that the RF isn't
>suited to telephoto lenses ? Again, why is this so ? Is it due to the
>'limited' rangefinder distance (58mm is it ? ) ?


Eric Welch
St. Joseph, MO

http://www.ponyexpress.net/~ewelch

A picture is the expression of an impression. If the beautiful were not in 
us, how would we ever recognize it?