jcolwell
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 p.1 #2 · Leica LTM and M lenses -- mounting to M4/3 or EOS? | |
Gunzorro wrote:
2) Is this lens adaptable to EOS mount, or is it similar to Leica M mount, and not able to focus at infinity?
Hi Jim,
It's similar to the LM situation. You can easily mount it on a M4/3 body, with "infinity focus", but you can only use it for macro work on an EOS body - no infinity.... Well, infinity is always out there, but you can't take a photo of it with an LM lens on an EOS body, unless you're a big MIB fan. 
It all comes down to the 'register', which is the distance from the lens mount to the camera sensor. In the old days, this was known as the 'film to flange' distance, whatever those obscure terms mean. 
The M4/3 register is 20.0mm, while the LM register is 28.0mm. This means that the LM to M4/3 adapter has to mount the LM lens 8.0mm away from the front of the M4/3 body. A simple mechanical adapter can do this. Of course, simple isn't always sufficient. The precision of adapter geometry is important, especially for wide angle lenses. You get what you pay for.
The EOS register is 44.0mm. That means you would have to insert the LM lens 44mm - 28mm = 16mm inside of the EOS mount to "acheive infinity focus". It is possible to get adapters for mis-matched registers, which use optics to compensate for this problem, but they invariably reduce IQ, and so negate the Alt advantage.
EOS (and Sony Alpha) have distinct advantages for using "35mm" Alt lenses, because their registers are shorter than all (or most of) the usual suspects; including, Nikon F, Contax C/Y, Pentax K and M42, Olympus OM, and some others. All of the "35mm" or "Full Frame" DSLR bodies can use medium format lenses, which have much longer registers. I prefer Mamiya M645 lenses, but that's a different story.
I can fix you up with a ton of info on this stuff, if you want.
Cheers, Jim
P.S. I just noticed that you have a Leica Thread Mount (LTM) lens, aka M39. The image of your adapter clued me in to this. The LTM register is 28.8mm, which means you have a whole 0.8mm for the LTM to LM adapter. No worries though, your new M39 to M4/3 adapter should do the trick.
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