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Re: [OM] M42

Subject: Re: [OM] M42
From: Christopher Biggs <chris@xxxxxxxxxxxxxx>
Date: 14 Apr 2000 08:29:11 +1000
Cc: olympus@xxxxxxxxxxxxxxx
grigorov@xxxxxxx moved upon the face of the 'Net and spake thusly:

> Hi all,
> I have a few M42 lenses worth keeping and found an adaptor for OLYMPUS. 
> Unfortunately
> the person couldn't tell me if it retains the infinite focus. Does anyone know
> the register of OM cameras? 

See here:
        http://www.smu.edu/~rmonagha/bronmounts.html
and here:
        http://www.a1.nl/phomepag/markerink/mounts.htm

and believe it or not on Lee Hawkins' Oly FAQ page!

OM and M42 are the same registration distance to within 0.5mm.  So
making a non-optical adaptor is very hard.

> Has anyone tried to adapt M42 to OLY? What are the
> things I should be aware of?

Does the adaptor have a lens in it?

For an M42 adaptor to keep infinity focus it needs to either

        a) incorporate a weak teleconveter arrangment (about 1.2x)

        b) be *really* *really* thin such that the M42 lens sits
           right up against the OM lens mount.

The lensed version can cause some vignetting with long-focus lenses.
Seems to be not so bad with normal lenses or telephotos.

I have an M42 to OM adaptor 10mm deep with a lens.  It maintains
infinity focus, with a teleconverter effect of about 1.25x.

If anyone has a sighting of the semi-mythical low-profile non-optical M42
adapter, I'm *really* interested in finding one of those. 

cjb

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