Yes. We Canon shooters are blessed with a shorter flange focal distance of the EF mount with 44mm, while the people in the Dark Side (Nikon) has a distance of 46.50mm. For this reason, very few lenses can be adapted and used on the Nikon with infinity focus, except Leica R lenses with a mount replacement. We should toss a glass of sake to the Canon engineers who came up with the relatively short mount distance. If you use Sigma SD cameras, good for you, because the Sigma SA mount is basically a Canon mount slightly rotated. In fact, Sigma uses the same protocals as Canon. You can actually modify the Sigma SD cameras and put on a Canon mount, and most Canon EF lenses will work (except IS).
So, which lens mount can be used with Canon EF? These are the ones I know and have used:
Nikon (F) -- Almost all Nikon lenses can be used without restriction except the weird fisheye lens from the 60s that you had to lockup the mirror to use. For G lenses, you need a special mount adapter that lets you set apertures.
M42/Universal -- Most lenses can be used on Canon without restrictions, but there are some exceptions. The one I know of is the Takumar SMC 50mm f1.4 on full frame, Myer Optik Primoplan 58mm f1.9 (on 5D), and may be a few others. The 5D (and possibly the 5D II and 5D III) are the most problematic.
Leica-R -- Most Leica-R lenses can be used on the Canon, but please refer to this great blog for the compatibility chart. In general, it's the wide angles that have issues.
Yashica/Contax (CY) -- Most are compatible, but few Contax lenses will hit the mirror on infinity. Again, Pebble Place has a great database with the compatibility chart.
Olympus OM -- As far as I know, there are no compatibility issues. All lenses can be used on the Canon. But then again, I don't have many OM lenses.
T/T2 Mount -- These lenses require a Canon EF to T/T2 mounts to use. I would say all are compatible with Canon. All T/T2 lenses do not have aperture automation, and always come with pre-set aperture.
Tamron Adaptall -- All Tamron Adaptall lenses should have no issues on the Canon when used with the proper adapter. Please note, as with the T/T2 mount lenses, there are mount adapters for most major cameras, including Canon EF.
DKL/Kodak Retina -- There aren't that many lenses with this mount and DKL lenses do not have aperture control on the lens, and no DKL lens is fater than f1.9. The adapter comes with aperture control. As far as I know, all DKL lenses work on the Canon. Voigtlander and Schneider are two major lens makers for the DKL mount.
Exakta (EXA) -- All the EXA lenses I have used can not focus to infinity because the adapters are not thin enough (can not be made too thin as there is only 1mm to work with). Avoid using Exakta lenses on the Canon unless you can find a seller who will guarantee infinity focus.
Rollei QBM (Quick Bayonet Mount) -- Like the Exakta, these adapters have trouble making the lenses focus to infinity on Canon. Avoid them unless you don't need infinity focus or the seller can guarantee it.
I think that's all the different mounts that I know of can be used with Canon. If you know of any others that I have left out, please let me know and I will update the list. Pretty much all medium/large format lenses can be adapted to Canon and other systems, but I have no experience with any of them so I won't talk about it.
Note that no range finder lens mounts are listed above. Range finder camera do not use mirrors that therefore the lenses can be pushed further into the mount without worry about the mirror, and this also means the flange focal distance is a lot shorter than SLRs.
If you use manual focus lenses mainly for video, those lenses (Leica, Contax, etc) that hit the mirror at infinity can still be used if you put the camera on Live-View, as this will flip up the mirror. Make sure you focus the lens to the closes focus distance before mounting it on the camera, or the mirror will hit the lens when you engage Live-View. Some brave souls will go as far as shaving part of the reflect mirror off in order to use their favourite lenses. I wouldn't do it, but other have done it.
Next time, we will have a look at the Micro 4/3 and Sony E-Mount in Part III.
An OM Mount lens on the Canon 1Ds that I used before.