Service for Canon LTM lenses?

[Sonnar Brian]

I think that is the culprit.

You could also give the retaining ring that is over it a little shave.

It's better than milling the mount.

Calipers, anyone?

 

[back alley]

i think it's fixed but i need to check in the light of day.

i tightened the screws on that silver ring, just a tiny bit needed and screwed the lens together again.
i usually check for infinity focus from my front steps to a building across the way.
hard to be certain in the dark but it seems to turn all the way to form an image now.

joe

 

[jlw]

Pictures of a disassembled Canon 50/1.4 are here.

The spacer/shim that determines the lens assembly's depth in the focusing mount is visible in the fourth picture. It's a brass ring that encircles the rear of the lens.

If the focusing mount lines up the rangefinder correctly at infinity, but the lens is focused to a shorter distance, the shim is too thick; if vice-versa, the shim is too thin. If it's too thick, you can remove a little by rubbing it across a sheet of fine abrasive paper on a flat surface. If it's too thin, you can buy very thin brass shim stock at a hardware store and cut a ring out of it with a hobby knife, using the existing shim as a template; then sandwich this with the existing shim.

(All this assumes you're checking on a known-good camera body, i.e. one on which the flange-to-film distance is known to be correct.)

 

[back alley]

i just stuck my head out the front doorway and focused my 135 on a building across the way. it's my standard for infinity focus testing.
and the damn thing works perfectly now!!

all i did was to tighten one of the 2 screws on the silver ring that seems to hold the shim down. and tighten just a tiny bit. so, other than actually unscrewing the lens apart and screwing it back together that was all that was done.
and now it focusses to infinity.
thanks for all the help gents.
i may have to head out into the morning fog with my 135 and play a bit.

joe

 

[Sonnar Brian]

If the retaining screws were sticking their little heads out, it could have hung the lens up when previously screws in. Tightening them would get them out of the way, and allow the lens module to screw in to the mount properly.

I make this stuff up as I go along.

 

[back alley]

'I make this stuff up as I go along.'

i knew it!!

whatever the explanation, i am pleased it works well now.

i have a roll of film that i took this morning while walking the dog in the early morning fog hanging to dry as i write this. (run on sentence?)
so, i'll know soon if it's sharp or not.

joe

 

[Kim Coxon]

Ssshhh Don't let everbody in on the secret. 😉

Kim

I make this stuff up as I go along.