Archived posting to the Leica Users Group, 1999/08/18

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Subject: Re: [Leica] Rangefinding with x2 convertors
From: InfinityDT@aol.com
Date: Wed, 18 Aug 1999 08:58:45 EDT

In a message dated 8/18/99 7:05:38 AM Eastern Daylight Time, 
doug@meditor.demon.co.uk writes:

<< The recent discussion concerning x1.4 and x2 convertors makes me
 wonder how one focusses the 'converted' lens? I'd always understood
 that 135mm was the practical limit for the Leica rangefinder, and that
 even the longer-based pre-war Contax finder had barely been able to
 cope with the shallow depth of field of the Zeiss RF coupled 180mm.
 
 Does the two-stop reduction in aperture reduce the DOF enough to match
 rangefinder accuracy?
 
 Regards,
 
 Doug Richardson >>

The 2 stop reduction in effective aperture does not increase DOF.  99.9% of 
the time I use my M-2x I am focused @ infinity, and also stopped down an 
additional 2 stops.  This is partly because the optics of the 2x suffer at 
the edges.  I've never tried using the 2x at closer distances, as I use it 
for isolating pieces of distant scenes.  I also use a little compact 
monocular to preview what I'm intending to photograph, as framing in the 
rangefinder patch doesn't make for a very detailed image.  As I've said, 
until Leica would actually design a telelconverter for the M, the only 
existing one is good for emergency use only IMO.