50mm Elmar 2.8 focusing adaptation

[breandan]

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I have just bought a 50 mm Elmar f 2.8 ( Number 16351xx) for use with my M6 from a reputable Leica shop and would be grateful if one of your experts would put my mind at rest with a slight worry I have.

I noticed that the half of the circumference of the brass tube which presses against the rangefinder wheel during focusing has been uniformly cut away by an amount that appears to be approx 1 mm. I wonder was this done during the original manufacture or later during some type of re-calibration. Has anybody observed something similar? I feel certain that the metal removed was not done by wear because the cut away part is neatly tapered at both ends.

I have not taken any pictures yet, but using a measuring tape to check the focus against the lens focusing scale (which is in metres) seems to be accurate. None of my other Leica lenses has this cut-away and I have not seen it in any Elmar picture.

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[christer]

I think you should stop worrying and go and take pictures, but not of brick walls or resolution charts.

 

These 1950s lenses (I do have one, and I use it very frequently) can be used to take great pictures provided the photographer has a good eye. They are, however, not quite up to today's lenses with regard to contrast.

[lct]

Show us a pic please.

[TomB_tx]

I noticed that the half of the circumference of the brass tube which presses against the rangefinder wheel during focusing has been uniformly cut away by an amount that appears to be approx 1 mm. I wonder was this done during the original manufacture or later during some type of re-calibration. Has anybody observed something similar? I feel certain that the metal removed was not done by wear because the cut away part is neatly tapered at both ends.

 

Yes - I still have lenses I bought new during that time period, and individual custom grinding the focus cam profile was standard manufacturing process at the time. It is more obvious on some than others.

[TomB_tx]

Here's my 2.8 Elmar, showing the production cam profiling that was typical during these years. I don't see this on my lenses from the 40s, but all my lenses from the 50s & 60s have this to some degree. (Very slight on my 69 fat tele-Elmarit, but obvious on my 50 & 35 Summicrons.)

As the exact focal length of each lens assembly could vary slightly, a single helical thread pitch wouldn't give exact focus for every lens. By grinding the focus cam surface to each lens they could both set the infinity focus and slightly slope the surface as needed for each lens (in theory) to focus well through its range.

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[breandan]

TomB_tx - many thanks to you for your informed reply and for your picture.

Over a liftime I have acquired several Leica lenses (and yes, I do take lots of pictures!) and never came across this design before. I was only anxious in case my new purchase had been adapted for some other purpose or to fit some other body. Again thanks for the information.

Breandan