Archived posting to the Leica Users Group, 1999/03/18

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Subject: RE: [Leica] Rangefinder + Super-wide lens
From: Jeremy Kime <jeremy.kime@bbc.co.uk>
Date: Thu, 18 Mar 1999 12:05:07 -0000

Chris, Thomas,
The observation about the viewfinder showing only a 24mm view is not
neccersarily correct.

Broadly the goggles magnify the view by 0.7x, that is how the original 50mm
frame on the M3 became a field of view for 35mm lenses.
I.e. 50mm x 0.7 = 35mm
Therefore if the converted 21mm lens (with goggles) keys in the 35mm frame
(on M2,4,5,6) you will see a 35mm x 0.7 = 24.5mm view.
I am sure the desired solution is for it to key in the 28mm frame (on M4-P,
M6) which then offers
28 x 0.7 = 19.7mm view.
This is what I've discussed with Tom Abrahamsson who has a couple of these
lenses converted. He says that the view is close enough for most purposes.
Reinhold Mueller is the Vancouver based technician that has 'specialised' in
these.

I contemplated this conversion as well, but as Thomas writes, there are
potential problems, the extra viewfinders can reduce clarity of image if not
in perfect clean condition. 
I would have hoped the conversion should address the aspect of incorrect
focus. The 35mm lenses which had the goggles fitted required a different
focusing cam to those 35mm without, anyone who has tried to use a 'goggles'
lens with the goggles taken off will find their pictures are unsharp except
at infinity, this is because the prisms affect the focusing optically.
Therefore if the 21mm conversion does not address this focusing cam issue
then I think it is hardly worth following, however, each to their own, it
may not worry some to have to estimate focus distances for such a wide angle
lens.

For myself I have had part of the rear ring of a Super Angulon milled off to
enable partial metering on an M6, for some this is heresy, to me it made
sense!

Jem
> -----Original Message-----
> From:	thomas boehm [SMTP:toboehm@yahoo.com]
> hello chris,
> 
> i can share my experiences with the 21 elmarit on the M6 - especially
> with  a "goggled" elmarit. 
> 
> : the viewfinder shows only a frame
> corresponding to a 24 mm. 
> 
> regards thomas
>