Adjusting for back focus, summicron 90

[aniMal]

Just got a canada-built summicron 90, a real bargain.

It is a little off at close range, infinity is spot on, but 2 meters is 10-15 centimeters off - behind the focus point.

The part of the focusing cam that adjusts close range would need to be raised just a little, would Leica then replace the cam if I send it in?

Are there any alternatives, like raising it and adjusting it myself...? Have been doing lots of 'impossible' things before, so this is not just desperate speculation.

I tested with some tape, and realize that the margins are very tiny indeed. The options as I see it are superglue or soldering. Used the first method on an old battered 90 2.8 years ago, worked just fine. Problem is just that I imagine the shutter of the M8 to be a bit more fragile, in case something breaks off...

Perhaps some paint? Any other suggestions?

Getting the right thickness will just need a very steady hand, and some trial and error...

[ferider]

Not sure which version you've got, sounds like it has a 360 degree cam.

You could shim the lens for close focus and then adjust for infinity, by grinding the cam ?

Make sure you test it with magnifier and tripod on M8 - you're at the limits of your EBL.

[aniMal]

Thats an option - easy to shim and would be a permanent solution. But, I feel a little reticent about grinding into the cam - has to be done perfect the first time.... And yes, it is the 300 something cam.

I think I will try to get some really thin paper, then glue it in strips to the cam so that it gets, say 1 layer at 5 meter, 2 at 2 and 3-4 at 1 meter. It will be hard, almost impossible to tear off because of the super glue - and can be sanded until it is quite flat.

Your soultion sounds like what Leica might to themselves - sure it is easy to keep a stock of shims and then grind it down. I guess they have some formulas to, telling how much to grind. Guess that should even be possible to deduct for myself......

[aniMal]

Checking & testing - managed to get it right at 2 meters!

It is the canada version with retractable hood by the way.

Tried a tiny strip of thin plastic glued to the cam with cyanoacrylate - still too much. The remaining layer of glue however, was just enough to get it right.

Only problem now is getting it smooth - perhaps paint is the best solution after all...

Anyway - it clearly is doable!