Sigma SD bodies... why not just switch mounts???

Why didn't I think of that...

Great idea. Jonathan, do you have a source for these mounts by any chance? I'd like one to use the KM Maxxum lenses.

(I'm going to guess that it's a little teensy bit more complicated than it might seem....)

http://www.d-shell.net/

Yeah, just take the mount out of an ald canon body and make it fit on a Sigma. Then simply use a hex editor to edit the firmware so this Sigma body actualy knows how to AF these things.

Yeah.... there's this new thing called manual focussing. Crazy huh?? Well, the sigma mount I SAW appeared simple enough. Just phillips screws. You'll lose AF or any lens control - but if you actually care about your glass - it should be irrelevant. Though I didn't consider that the body might NEED some sort of electrical signal coming FROM the lens. Does anyone know if this mightb e true - or would one have to ask a Sigma Tech. At the very least though - all you skeptics - I'd read somewhere (here or DP review) that one could also get adapters (although I really can't understand how that would work since it would change the lens to sensor distance.

Perhaps it's a question for Mr. Grimes to answer...?

J.

Given that the flange to film distance is likely to be different for Canon and Sigma - I seem to remember reading that Canon's was one of the lowest, hence the availability of adaptors to use lenses such as Leica R - I can't see this having a chance of working.

Will the replacement mounts be the same diameter and thickness, have the same size screw holes, in the same places?
Will the rear of the non-Sigma lenses clear the Sigma electronics contacts and the dust shield right behind the mount?
With no electronic connections, how will you stop down the lens aperture, or will you be content to always shoot wide open?
And what's so great about the Sigma body in the first place to make any of this worthwhile?

Well, it's actually more common to have the odd Canon lens converted over to Sigma mount. The typical SD body owner already has some Sigma mount lenses. There are several people who do this and sell the converted Canon lenses on a popular (but unmentionable) auction site (hence refered to as PAS).

The conversion of the body to Canon mount is much easier than Nikon mount. Canon and Sigma share a 44mm registration distance, so you don't have to "build up" the mount to hit the 46.5mm Nikon registration. The Sigma AF protocol is a copy of the Canon protocol (serial messages, contact arrangement, etc) so if you just connect a Canon flange to a Sigma body AF, exposure control, and metering all work. A Nikon lens will be restricted to manual focus and stopped down metering.

You'll need a Canon service manual to provide the correct part numbers for ordering. You can find these online in PDF form, or for sale on PAS. You'll need the lens mount, several spring clips that attach to the back (separate part numbers). You probably want an EOS3 manual, I think that's the first one where the mount is a decent quality solid metal.

If you don't want to permanently deface the SD body, you'll also need a front "bullnose" from Sigma parts and service, so you'll also have to track down a Sigma service manual.

When the recent UK price reductions for SD10 hit the US, I'm going to try this myself.

Have fun.

I think Sigma would benefit if they scrapped their mount and switched to the 4/3 mount used by Olympus. It's an open standard and wouldn't cost them anything to licence it. If they did that then possibly they might sell some cameras in the U.S.