Re: 40mm Summicron-C

[Paul Schliesser <paulsc@eos.net>]

>What is the word on using the 40mm (made for the CL) on an M-series? Aside 
>from lacking specific frame-lines, does it perform up to the name 
>"Summicron"? 
> It is extremely compact. I saw one reference to its being a great snapshot 
>lens, but another reference implied the M's focusing cam does not work real 
>precisely with it. Rumor? Fact? Significance? Many TIA.

Robert,

From what I understand, the C lenses have a beveled focusing cam, which 
will not correctly contact the focusing wheel, on the end of the lever, 
inside the throat of a normal M body. (The normal M lenses have flat 
surfaces on their cams.) This will effect focusing accuracy since there 
seems to be some uncertainty as to where the wheel will contact the 
bevel. This in turn will alter the distance that the rangefinder 
indicates. I guess you could scale focus and be OK.

I never understood this, since it seems that the wheel would ride on the 
top edge of the bevel, unless the cam diameter is much smaller than those 
on the M lenses. If it is smaller, then the wheel would ride lower down 
and it would be off. Also, since M lenses work correctly on the CL, it 
seems odd that the C lenses would not work the other way.

I have not tried one of these lenses on a normal M body, myself. This is 
just what i remember reading in a manual or book.

From what people have said, the C lenses are excellent.

- - Paul