Leica LTM Help with marking on summar

Leica M39 screw mount bodies/lenses
ChrisLivsey

ChrisLivsey

Veteran
Local time
7:26 AM
Joined
Jul 3, 2007
Messages
2,143
View My Gallery
For a project I have in mind I have recently acquired an uncoated 5cm f2 Summar (217254 serial). There is a letter "A" engraved/stamped on the rear of the infinity lock. Is this usual and does it have any significance ?
 

Attachments

  • SummarRFF.jpg
    SummarRFF.jpg
    190.5 KB · Views: 0
I am not joking here: My Summar has an incribed letter B at the same location. I took out my lens, and I used a magnifier.

Maybe it is the initial of the worker who put together the lens.
 
Sigh, this thread just cost me 3 minutes of my life....... 😉

My summar from '36 has an A, and '39 has a 7.
 
ChrisLivsey said:
For a project I have in mind I have recently acquired an uncoated 5cm f2 Summar (217254 serial). There is a letter "A" engraved/stamped on the rear of the infinity lock. Is this usual and does it have any significance ?
Click to expand...
It is simply an indication of the exact focal length of your lens. "A" means 52.2mm focal length.

Erik.
 
I never heard about this fact. Thanks for the information. My lens is then not exactly 52.2mm.
 
Last edited:
The pitch of the threads in the helical differs for each of these marks, and has to match the lens cell.

Very important to a repair person.

Also important in macro-photography to compute exact reproduction ratios based on lens extension.

My great Summar (324xxx) has what looks like a 7. My worthless dog Summar (346xxx) has a B, or perhaps an 8.

I'm surprised that any of the lenses used a letter.
 
At some point Leitz stopped making bunches of slightly different helicals (if they ever did) and started grinding a slight second cam into the brass ring that contacts the rangefinder's roller.
 
Al Kaplan said:
At some point Leitz stopped making bunches of slightly different helicals (if they ever did) and started grinding a slight second cam into the brass ring that contacts the rangefinder's roller.
Click to expand...

Dear Al,

Indeed" 'if they ever did'. This is such a fantastically complicated solution (as compared with camming the lens, which is all I knew about) that I'd be amazed if ever they did.

I'd never heard of if -- though that doesn't necessarily mean much -- but from the point of view of inherent probability, it sounds deeply unlikely.

Cheers,

R.
 
Camming the rangefinder cam works on M mount lenses, where the indexing of the lens to the camera is predictable. It doesn't work very well on thread-mount lenses, since the rotational indexing of the lens to the camera is not highly predictable. The infinity mark could be anywhere between noon and 2 O'clock on the front of the camera. You can do it, but there's a compromise in the accuracy of the results.

I've certainly read authoritative materials stating that Elmar 50/3.5 lenses had various pitches of focusing helical threads.

The mapping of the code numbers and letters to actual focal length isn't very rational. There's some information on it in Puts's book, and they are all over the place.
 
John Shriver said:
Camming the rangefinder cam works on M mount lenses, where the indexing of the lens to the camera is predictable. It doesn't work very well on thread-mount lenses, since the rotational indexing of the lens to the camera is not highly predictable. The infinity mark could be anywhere between noon and 2 O'clock on the front of the camera. You can do it, but there's a compromise in the accuracy of the results.

I've certainly read authoritative materials stating that Elmar 50/3.5 lenses had various pitches of focusing helical threads.

The mapping of the code numbers and letters to actual focal length isn't very rational. There's some information on it in Puts's book, and they are all over the place.
Click to expand...

Dear John,

Ah, that makes sense -- but I'm still surprised, because the degree of rotational focusing travel on most old lenses is quite large, and I don't think the variation in position would have been anything like as great (noon to 2 o'clock) when the cameras and lenses were new -- at least, not after the mid-30s when the faster lenses started to come in. After all, focal lengths other than 50mm are cammed, and must still depend on rotational positioning. Can you recall the sources?

Cheers,

Roger
 
You must log in or register to reply here.
Back
Top Bottom