M39 RF lens on M42 SLR?

[raftman]

I've seen quite a few M39 to M42 adapters online (including evilbay), which supposedly allow you to use any of the M39 lenses on any M42 body. I found the idea interesting, thought it would be cool to use an I-61 L/D on a Zenit-E or something like that. At the same time I also read it's not that simple in most cases, and that it would be difficult to actually make a set-up of that sort fully functional.

So that brings me to my question. Do these adapters really deliver what they promise? Or is it not possible/practical to pull it off?

[erikhaugsby]

No, it is in no way possible without sacrificing infinity focusing. The backfocus of a Leica is somewhere around 28.6mm (correct me if need be), while the backfocus distance of many SLRs can be as much as twice or three times that. This discrepency will greatly reduce the range of focus, though to what extent is determined by the camera used.
Additionally, since there would be no connections between the lens and camera you would need to use stop-down metering; this brings on the whole consortium of joys of looking through a lens at f/16 and trying to frame while metering...

[dazedgonebye]

I believe the m39 adapters you've seen may be for adapting old Zenit SLR lenses.

[erikhaugsby]

It is possible that you mistook them for M42 to M39 adaptors, which do exist and do work (albiet many, if not all, are without rangefinder focusing).

[raftman]

Well that was part of the question. Some sellers claimed the adapters can be used for making ANY M39 lens usable in an M42 body, I took it as implying that this also includes RF lenses in an SLR. So that was what I was asking about the feasibility of.

[rbiemer]

If you get/have an M39 SLR lens, then you should be ok to use it on an M42 SLR. If you want to shoot macro, then using RF lenses might be ok. Pay close attention to how deep into the SLR body the rf lens protrudes. You sure don't want to have the mirror in the SLR trying to rise and smacking into the back of the lens.
I find it helpful to focus wide open, then stop down, meter and shoot.
Rob

[ZorkiKat]

The Industar-61 L/Z (note "Z" as opposed to "D"which is for rangefinders) was supplied in both Zenit M39 and M42 mounts. Yes you can use any M39 thread lens with this adapter, but those for Leica type cameras can only be used for extreme close-ups. The maximum focus distance in these instances would be something like 10 to 15 cm.

Note too that the Zenit M39 lenses have a slightly shorter register than SLR M42 mount lenses : 45.2mm for the former vs 45.5 of the latter. True infinity focus may not be possible with adapted lenses.

In my experience, the brass Russian M39-M42 adapters tend to have slightly thicker threads which prevent them from screwing fully into an M42 camera mount.

Jay

[Abbazz]

Rob,

As Erik said, it is not possible to mount a LTM lens on any 35mm SLR, with the exception of few Leica lenses designed to be used on the Visoflex attachment. The much shorter registration distance of usual LTM lenses would not allow focusing at usual shooting distances on a SLR without the use of a specially designed retrofocus adapter, which would alter significantly image quality. Contrary to what the sellers say, the common type adapters sold on eBay will not allow to focus on objets located more than a few centimeters from the front of the lens. Even for "macro" shots, one would get images with lots of optical defects, as LTM lenses are not corrected for close focusing. I really don't see the point in buying one of these adapters, as you can get a much more capable Takumar M42 lens for less money.

Cheers,

Abbazz

[rbiemer]

I actually bought an adaptor ring for a much sillier reason; I got a set of M39 SLR extension tubes to use a part of a pinhole lens for my LTM cameras. I decided that I wanted to be able to use the same "lens" on my Pentax so I got the ring instead of K-mount extension tubes. I had a M42 to K mount adaptor already and so in a bit of a "mad scientist" moment thought I would see what could see through my LTM lenses. Not much, in fact. And as you point out there are many better choices for macro work!
Rob