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LTM / LSM / L39 correct naming
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PostPosted: Wed Oct 31, 2018 8:52 am    Post subject: LTM / LSM / L39 correct naming Reply with quote

Hello everybody,
Is there a consensus on correct LTM naming ? Is M39 still considered as correct ?

Sorry to ask again but search engine seems to don't work on the forum for me...
Thanks a lot !


PostPosted: Wed Oct 31, 2018 9:26 am    Post subject: Re: LTM / LSM / L39 correct naming Reply with quote

Musashichan wrote:
Hello everybody,
Is there a consensus on correct LTM naming ? Is M39 still considered as correct ?

Sorry to ask again but search engine seems to don't work on the forum for me...
Thanks a lot !


The problem with such a "generic" description is that it really only refers to the thread used - "Metric 39mm" - there's no account for the back focus of the lens (or rangefinder coupling, for that matter).

39mm threads were/are used on the early Leica rangefinder cameras, which spawned a generation of clones, copies and look-a-likes, but the same thread was also used on enlarger lenses (possibly because camera lenses were already available in this fitting) as well as early Zenit slr's and some other cameras, eg. Paxette, I believe, except these have a different back focus, so cannot be conventionally used on a Leica (or compatible-mount) camera.

So, for my money, there's room for L39 or LTM, denoting a specific type of camera lens, possibly rangefinder coupled, and a more generic M39, possibly indicating "I'm not quite sure what it fits", as well as a couple of "classified" descriptions, such as "39mm Zenit screw" or "39mm Paxette mount".

Just my thoughts - YMMV Wink


PostPosted: Wed Oct 31, 2018 10:45 am    Post subject: Re: LTM / LSM / L39 correct naming Reply with quote

kypfer wrote:
Musashichan wrote:
Hello everybody,
Is there a consensus on correct LTM naming ? Is M39 still considered as correct ?

Sorry to ask again but search engine seems to don't work on the forum for me...
Thanks a lot !


The problem with such a "generic" description is that it really only refers to the thread used - "Metric 39mm" - there's no account for the back focus of the lens (or rangefinder coupling, for that matter).

39mm threads were/are used on the early Leica rangefinder cameras, which spawned a generation of clones, copies and look-a-likes, but the same thread was also used on enlarger lenses (possibly because camera lenses were already available in this fitting) as well as early Zenit slr's and some other cameras, eg. Paxette, I believe, except these have a different back focus, so cannot be conventionally used on a Leica (or compatible-mount) camera.

So, for my money, there's room for L39 or LTM, denoting a specific type of camera lens, possibly rangefinder coupled, and a more generic M39, possibly indicating "I'm not quite sure what it fits", as well as a couple of "classified" descriptions, such as "39mm Zenit screw" or "39mm Paxette mount".

Just my thoughts - YMMV Wink


Thanks for your opinion, precious. I know the history, the back ground and specifications but i just want to have the general opinion ont the names given to the different mounts.
Want to know if there is a consensus !


PostPosted: Wed Oct 31, 2018 1:09 pm    Post subject: Re: LTM / LSM / L39 correct naming Reply with quote

Musashichan wrote:

Thanks for your opinion, precious.


Thanks for the epithet ... I'm sure you're very sweet as well Wink


PostPosted: Wed Oct 31, 2018 5:28 pm    Post subject: Reply with quote

There is no real consensus on 39mm thread mount lenses.

"LTM"- Leica Thread Mount implies that the lens is made for the Leica RF camera specification. This is different from Zorki and Fed RF 39mm Thread Mount cameras, Pax 39mm RF mount, Zenit SLR 39mm, 39mm half-frame, 39mm enlarger lenses, and anything else not built to the Leica RF standard.

The LTM standard "as best I can find" has a 28.8mm flange and is calibrated for 51.6mm focal length. The Fed and Zorki have a 28.8mm flange, but are calibrated for a 52.4mm focal length. They are not LTM. The many Japanese cameras and lenses (and a few English, American, and other cameras and lenses) were built to the Leica LTM spec.


PostPosted: Wed Oct 31, 2018 6:30 pm    Post subject: Reply with quote

I think that the Canon L39 is also slightly different fronm the LTM . There is no problem to use the same adapter nowadays.


PostPosted: Wed Oct 31, 2018 7:25 pm    Post subject: Reply with quote

Canon S-II, introduced in 10/1946, is the first Canon built to the Leica standard. Production of the Canon unique mount ended in late 1946. Any encountered would be priced out of reasonable reach if the seller knows what it is.

I picked up a Non-RF coupled Canon 13.5cm F4 a short while ago for $50. Sometimes you get lucky.


PostPosted: Thu Nov 01, 2018 9:38 am    Post subject: Reply with quote

My main issue is between LTM and M39 for reflex, as M39 has been long used for Leica, incorrectly but already today (even on Wikipedia and adapters) M39 is still used for Leica and leads to 90% of mistakes when choosing a lens (as a seller i face this every week) for a camera or for the adapter ring...

Is for someone M39 still correct for you when talking about LTM?


PostPosted: Thu Nov 01, 2018 11:56 am    Post subject: Reply with quote

For most camera forums that have Leica discussions: no, the members understand LTM to be the term to use for a camera or lens made to the Leica standard. "Before Ebay", where you bought from a camera store- there was not the confusion of lenses from the former Soviet Union countries being available on the click of a button. Same with the "I have no idea of what this lens is, but it is made for a Leica because I measured the threads" sellers.

LTM, Leica Thread Mount, is the correct term to use when selling a lens, or buying a lens. Anything else- unless you recognize it, buy LOW, and be prepared to use it as a paper weight. I have a couple of the latter.


PostPosted: Thu Nov 01, 2018 8:47 pm    Post subject: Reply with quote

LTM describes both the thread & the registration while M39 just describes part of the thread (the thread pitch is needed to fully categorize the thread something that is becoming a pain with M42 as both 0.75 & 1mm pitches are in common use for photography) - I have quite a few lenses with M39 thread but no LTM lenses.

Surprisingly I've found some excellent 2 part LTM-MFT adapters that are even cheaper than generic M39-M42 ones, or other MFT adapters, making them an irresistible option for lens hacking Smile


PostPosted: Tue Nov 06, 2018 5:46 pm    Post subject: Reply with quote

M39 is a misnomer, since it would imply metric threads. The Leica Thread Mount is a "mutt", while the thread diameter is 39mm, the thread pitch is 26 threads per inch. The lathes they had available to cut them must have only had "English" lead screws for threading.

The earliest Canon rangefinder cameras used a metric thread pitch, and would bind with Leica lenses. They then changed a sloppier thread cutting on the cameras that could accept either type of lens.


PostPosted: Fri Nov 09, 2018 8:17 pm    Post subject: Reply with quote

LTM/L39 is rangefinders; M39 SLRs.

Enlarger lenses are another thing, but they're easy to identify.

Pitch on other lenses is an issue and a risk when you buy online lesser known lenses.