Is LTM and M39 the same thing?

[longw]

Hi,

I remembered I read somewhere LTM (Leica thread mount) and M39 lens mount are actually different mount types. FSU RF cameras use LTM mount lens. Zenit used M39 mount for its early SLR, like zenit S . But recently I have seen several times someone said LTM and M39 are the same. I think they are wrong. Am I right? 😕

tao

 

[Nickfed]

Yes you are right. The early Zenit you allude to used the same M39 thread but the flange to film distance was greater. As a consequence, the LTM lenses would fit but would not focus on infinty as they were too far from the film.

 

[payasam]

LTM is Leica Thread Mount and cannot be anything else. The fact that the same 39 mm thread was used for SLR lenses can lead to confusion: because "L39" and "M39" are often used interchangeably. The simplest way to identify a lens made for an SLR is probably by the absence of a focussing cam.

 

[Spyderman]

M39 is designation of the thread: 39mm. This is the same on leicas and on zenits. To avoid confusion the leica mount is often called L39 or LTM or LSM... but not by definition...

 

[jarski]

I read somewhere Nikon, when they started their business after war. they adopted LTM, but changed it slightly (why!?), so its not fully compatible with original LTM.

now, Nikon RF lenses that are sold in eBay and elsewhere. those are not compatible with any other RF cameras, but Nikon. right ?

 

[xayraa33]

I read somewhere Nikon, when they started their business after war. they adopted LTM, but changed it slightly (why!?), so its not fully compatible with original LTM.

now, Nikon RF lenses that are sold in eBay and elsewhere. those are not compatible with any other RF cameras, but Nikon. right ?

Nikon used the Contax bayonette mount, but the lenses are to the Leica 51.6 mm standard not the Contax 52.3mm so only wide angle Contax lenses will focus ok on a Nikon RF camera at the larger apertures .

 

[Murray Kelly]

My understanding is the very early LTM confused everyone by using an Imperial (english) thread. It was from memory 25 threads / inch. It was assumed incorrectly to be 1mm / 25mm but wasn't. I have an early FED-1 here that won't accept modern LTM lenses because of this. An inch is 25.4mm and the difference is enough, even with only the few threads to bind with modern LTM lenses. I can get another industar to fit, but it's a bit of a struggle. None of the J-8 lenses etc won't screw in.

Murray

 

[Jocko]

My understanding is the very early LTM confused everyone by using an Imperial (english) thread.

I believe this is so, although as they were the first, those who were confused had only themselves to blame 🙂 Leitz made microscopes, so the LTM is based on a 26-turns per inch Whitworth thread, which remains the standard for much laboratory equipment to this day.

Cheers, Ian

 

[longw]

Hi Murray,

You are quite right. I just found some information. So LTM is 39mmx26 turns/inch while M39 39mmX26 turns/mm.

I right have a M39 industar50 and a FED 2. Just tried to screw the lens into FED, no problem. But the infinite focusing is not working. Maybe M39 lens can be used on LTM cameras for macro photographying.

This need to be clarified especially to ebay sellers.

tao