[Leica] 21mm M Biogon question

[henningw at archiphoto.com (Henning Wulff)]

At 7:18 PM -0400 6/24/08, A. Lal wrote:
>Hello Everyone,
>
>I picked up a 21mm Biogon/2.8 for the M mount and need a filter to 
>protect the front element. Will a regular 46mm UV filter do, or will 
>I need to get a slim filter to prevent vignetting  in the corners?
>
>Thanks in advance
>
>Regards,
>Akhil

Easy to check on a film camera. Open the back, lock open the shutter 
on B and look through from the front. If you can see light coming 
through the corners of the film gate from all around the aperture, 
there is no vignetting. If the filter rim starts blocking the view of 
the film gate corners before the aperture does, you've got vignetting.

I doubt there's any vignetting with any filter. There definitely 
won't be any vignetting with the M8.

Heliopan slim filters have threads on the front. Some others don't.


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