Will it focus properly?

[bennyng]

Hi guys,

Saw this 'reconstructed' 100mm f/3.5 on ebay. 110378478805

The front with all the lens element are from the early type. The focusing helicoid is from the later all black type.

Will a lens like that still focus properly?

Cheers,

 

[le vrai rdu]

may be yes maybe no
I wouldn't be surprised it worked, but it need a try 😉

 

[ferider]

if it was shimmed properly, yes.

 

[Sonnar Brian]

What Roland said- as long as the optics module has the correct shim, and that is not hard to do.

Above is with a CZJ SOnnar in a J-3 mount, shimmed for the Leica.

Not hard to do. Any decent repairshop that can CLA a lens can do it.

 

[John Shriver]

Now, I don't know what Canon did, but I know that Leica measures the focal length of lenses after manufacture, and classifies them into focal length ranges. For each range, there is a different focusing helicoid and rangefinder cam, calibrated for that range of focal lengths. For lenses with removable heads, Leica would mark the serial number on the mount as well as the lens head.

If Canon did the same (which is rather likely, although they used statistical process control long before Leica did), then this lens could very well be of a focal length different than the focusing mount is calibrated for. In that case, even if shimmed properly for infinity focus, the focusing could be inaccurate at close distances.

It's a mutt, I'd stay away, far away!

 

[Philip Whiteman]

Having unwittingly bought a 90mm Summicron assembled from the focussing mount of one example and the optical head of another I can only agree with John's wisdom!

 

[Sonnar Brian]

The big IF was the lens collimated properly. A proper re-fit would test the focus close-up, mod-range, and at infinity. If the focus is off, then the rear module of a lens can be adjusted as well. Not too many people actually do this last step. It is not that hard to do.

I'll keep a watch on the lens.

 

[bennyng]

The big IF was the lens collimated properly. A proper re-fit would test the focus close-up, mod-range, and at infinity. If the focus is off, then the rear module of a lens can be adjusted as well. Not too many people actually do this last step. It is not that hard to do.

I'll keep a watch on the lens.

I'm no expert on this kind of stuff and certain not too handy with my hands.

Anyway, thanks guys for all the good comment and advice, especially Brian and John.

I think I'll pass on this mutt for this round.

Cheers,