Even for lenses designed at the outset to have different mounts (eg:
Vivitar, Kiron, Tokina) changing from one mount to the other was never
simply a matter of popping off the old mount and popping on the new. If
you look at the parts diagrams you'll see that there are numerous parts
involved in making the switch.
As Jeff says, there is a fundamental difference in register distance
between Practica B and M42 with the Practica lens falling more than 1mm
short of reaching infinity. I wouldn't say that it can't be done but
there would be a lot of very precise metal surgery to be done.
Chuck Norcutt
On 11/28/2010 12:49 PM, Jeff Keller wrote:
> Praktica has a register distance of 44.4 while M42 has 45.46. The thickness
> of what you remove from the lens would have to be 45.46 - 44.4 = 1.06 mm
> thinner than what you add back on to maintain infinity focus.
>
> http://www.graphics.cornell.edu/~westin/misc/mounts-by-register.html
>
> Also, your m42 mount camera might have limitations on how far the back of
> the lens can extend into the camera. If the Practica lens has an auto
> diaphragm you would probably have to use manual stop down.
>
> Jeff Keller
>
> -----Original Message-----
> From: AS [mailto:alizookoman@xxxxxxxxx]
> Sent: Sunday, November 28, 2010 7:22 AM
> To: Olympus Camera Discussion
> Subject: [OM] Changing lens mount
>
> I want to try changing lens mounts. Is this as easy as removing the old
> mount and popping in the 'new' mount? Instead of screwing in the new mount I
> am thinking of using some type of glue. The lens mount is PB mount right
> now and I want to convert to M42 mount.
--
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