Converting to a Coded M Lens Mount

[Double Negative]

Ok, I'm a tad confused. The code for:

APO-Summicron-M 50mm f/2 (VI) 11141 - 110101 50/75 and

APO-Telyt-M 135mm f/3.4 11889 - 110101 35/135

are the same. Wouldn't the exif data be wrong for one of the lenses?

Nice catch! First instinct is to say, "why yes!" But no. Here's why.

In order to "code a lens" you need two things. First, the 6-bit code that we all know and love... But also the framelines that are brought up! As you can see, both lenses bring up different framelines - and thus, are different.

 

[Double Negative]

Nicely written up.

I'm glad you mentioned tightening the screws opposite to opposite and gradually.

Two observations come to mind. When I did mine a few months ago one of my Jin adapters had some flash in the screw holes. This was just enough to force the adapter off centre despite careful tightening, and the result was that the focusing tightened up on my 50mm Summicron. I drilled the holes out a fraction, but putting a fine round file into the holes would do the same job. This fixed it, and I can hardly complain given the bargain price.

But this led to a second thought, the focusing of my 35mm Summicron had always been slightly notchy and it occured to me it may be for a similar reason. So I simply loosened the screws of the original flange and did them up again gradually and in the right order, and lo and behold the lens became slick and smooth. So for notchy or stiff focusing lenses the first course of action may be to just check the flange screws are tightened properly.

Thanks! I used to build race engines - old habit.

That's interesting regarding the flash/burrs. There was a hint on mine as well... But I merely ran a fingernail around any edges and into the notches. I didn't notice anything in the countersunk screw holes though. I'd say a file would be a better way to go for cleaning them up than drilling. They're not Milich mounts, that's for sure - but like you said - they're also $15-20!

I can see how certain lenses would improve by re-torquing the mount. It does get a lot of abuse over time. Depends on what the screws go into and how deep, etc. I did try this on a couple of balky ZMs, but nope - still got that crap wobble!

 

[Vivek]

Has anyone put a 6 bit code on a Rokkor 40/2? Any pics would be appreciated.

 

[zombii]

Can I assume that the machining of these mounts is of the correct and consistent thickness since I haven't seen any mention of problems along that line?

 

[Double Negative]

Can I assume that the machining of these mounts is of the correct and consistent thickness since I haven't seen any mention of problems along that line?

This did worry me, having had a bad experience with such eBay LTM/M adapters centering the lens off the middle... Which is arguably the correct behavior, but not what I was looking for.

I haven't had any issues so far, and haven't come across any others. So far, so good.