[Leica] Canon 5D + Leica Lens Exposure Question

[rbaron at concentric.net (Robert D. Baron)]

Frank Fillipone writes:

> I am very confused...and quite interested....
> 

Yes.

> Is this the way Canon locks in their  user base?  Sort of later day mount
> patent?

No.

Third party lens manufacturers (such as Sigma and Tamron) make lenses 
that have the Canon mount and are equipped to electronically communicate 
with Canon bodies, film and/or digital.

Leica does not make a lens with a Canon mount or Canon electronic 
communications.

To use a Leica R lens on a Canon body you must use a third party (e.g., 
Cameraquest) adapter that merely allows you to mount the R series lenses 
(well, most of them) on a Canon body.  There is no electronic 
'communication' between the lens and the body.

The body doesn't know what is attached to it, but its electronic light 
metering does recognize that light is coming through and thinks 'well, 
I'm set for ISO 400 and there is X light hitting me so I'd better use Y 
shutter speed'.

Hope This Helps.

--Bob