Calibrate Canon 135mm 3.5 LTM?

[alfisti71]

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Anyone know how to calibrate the focusing on the Canon 135mm 3.5 LTM? Is it easy to do as a DIY? I have an M 240 with EVF, and I can see that focus is WAY off on the lens I just got. Thanks

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[spydrxx]

What exactly do you mean that the focus is way off, that the focus scale on the lens doesn't match the actual subject to camera distance? It shouldn't be way off if you are using a correct thickness LTM->M adapter. I had two situations over the years with LTM lenses on M bodies. In one case somebody had taken the lens apart presumable to clean the elements and reassembled it with an element reversed DAG corrected that and recalibrated it), and the other case merely involved my slightly readjusting the focusing ring on the lens so the infinity hard stop was correctly positioned at the infinity mark (merely loosening three set screws, shifting the ring, and retightening them).

[alfisti71]

5 hours ago, spydrxx said:

What exactly do you mean that the focus is way off, that the focus scale on the lens doesn't match the actual subject to camera distance? It shouldn't be way off if you are using a correct thickness LTM->M adapter. I had two situations over the years with LTM lenses on M bodies. In one case somebody had taken the lens apart presumable to clean the elements and reassembled it with an element reversed DAG corrected that and recalibrated it), and the other case merely involved my slightly readjusting the focusing ring on the lens so the infinity hard stop was correctly positioned at the infinity mark (merely loosening three set screws, shifting the ring, and retightening them).

I just tried a new adapter... and you are right. It's perfect on the other adapter. They LOOK identical but they are apparently not. The "bad" one is a Fotodiox with coding dots. Baffling to me how it could be machined wrong. But apparently so. Thanks 

 

[AZD]

By chance can you please let us see which adapter worked correctly? Specifically I am interested in how the lens and cam actuating surface are positioned when mounted on the M body. 
 

I have had similar problems with a Canon 85mm f2 LTM. The adapter is the correct thickness, but the lens is approximately 30 degrees counterclockwise from perfectly upright when mounted. For many normal and wide lenses this does not matter as they have a uniform 360 surface which controls the rangefinder cam. However, lenses which use a “cam follower”, kind of a finger at the lens’s twelve o’clock point, may not register correctly with the rangefinder if noon comes to rest at 11 on the camera body, if that makes sense…

 

My solution so far has been to build up a very thin layer of aluminum tape on the lens’s cam follower, which works but kinda annoys me.

One last comment, which is a slightly different matter - if you find that the lens and rangefinder agree but image sharpness is off, there may a way to move the lens cells forward or backward, like shimming or rotating the cell on its threads. I don’t know about the 135, but my 85 is like this. It is currently set for precise focus at 1m wide open, but infinity wide open is off… but who cares? Seems like a decent compromise.

Anyhow, sorry for rambling. 

 

 

 

[spydrxx]

AZD - many LTM adapters have 3 tiny screws spaced equally around the perimeter allowing you to rotate the lens in the adapter so it has the correct orientation on the camera.

[AZD]

Spydrxx, thanks for the tip. I’ll look out for such an adapter. The few I have are admittedly inexpensive adapters with no adjustment possible. 

[UliWer]

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vor 7 Stunden schrieb spydrxx:

….many LTM adapters have 3 tiny screws spaced equally around the perimeter allowing you to rotate the lens in the adapter so it has the correct orientation on the camera.

It would be interesting if you could name or better show such an LTM-adapter.

Fact is that none of the original Leitz LTM-adapters had such a device - and for sure it is not necessary. A normal LTM lens will adjust properly with any of these adapers. 

[frame-it]

7 hours ago, spydrxx said:

many LTM adapters have 3 tiny screws spaced equally around the perimeter allowing you to rotate the lens in the adapter so it has the correct orientation on the camera.

which LTM  adapters have these 3 screws?

[UliWer]

vor 14 Stunden schrieb AZD:

but the lens is approximately 30 degrees counterclockwise from perfectly upright when mounted. For many normal and wide lenses this does not matter as they have a uniform 360 surface which controls the rangefinder cam. However, lenses which use a “cam follower”, kind of a finger at the lens’s twelve o’clock point, may not register correctly with the rangefinder if noon comes to rest at 11 on the camera body, if that makes sense…

If you attach such a lens on an original LTM camera you‘ll find out that it will not be „perfectly upright" but just tilted a little bit to one side. This is no fault but a „feature“. With LTM bodies it was usual to use separate finders like the VIDOM or VIOOH which had a long „nose“ protruding in front of the camera. So the finder would cover the view on the scale if the lens was „perfectly upright“. Therefore the lenses had a certain tilt to ensure that you could see the scales without obstruction from the finders. 

Edited March 25, 2023 by UliWer

[UliWer]

Here you see a 50mm Summicron with original LTM mount on an original LTM mount Leica:

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The index for the distance is certainly not in the "perfect upright" position but set off to the left. Could you expect that an adapter would place the lens in a different position?

And here you see the reason for this "wrong" position:

The finder's long nose would obstruct the view for the index, if it was "perfect upright".

With the "wrong" position tilted to the left there is no such obstruction. 

You'll see the same with any Leica 50mm lenses on any Leica LTM bodies. 135mm lenses don't have the tilt, but the index will be in perfect upright position. They don't need it, since the shaft is so long and the index is at the lenses front so it can't be obstructed by the finder.  

If your adapter is precise it will reproduce the same position of the lens as it was originally on the LTM body. 

 

Edited March 25, 2023 by UliWer

[UliWer]

Here the Canon Lens 1:1.9/85mm on the Leica IIIf:

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Also no "perfect upright" position, but a tilt to the left. Same reason.

Canon knew what they did when the "copied" the LTM system in their beginnings. 

 

[UliWer]

vor 55 Minuten schrieb UliWer:

You'll see the same with any Leica 50mm lenses on any Leica LTM bodies.

That is not correct:  the index of the 5cm Elmar is indeed in "perfectly upright" position. As the Elmar's scale is flat on the camera's front you cannot see it looking from above but have to look frontally at it. Therefore the offset position of the index would not have made much sense.  

Edited March 25, 2023 by UliWer

[spydrxx]

Whoops, my bad - must have been an age related brain fart😁. I was thinking of adapters to mount LTM lenses to mirrorless bodies which have the screws to allow centering of the focus scale to the bodies.

[dpitt]

4 hours ago, UliWer said:

It would be interesting if you could name or better show such an LTM-adapter.

Fact is that none of the original Leitz LTM-adapters had such a device - and for sure it is not necessary. A normal LTM lens will adjust properly with any of these adapers. 

I only have seen this kind of adjustment screws on adapters for MFT. Might be available for other mirrorless systems too. Of course in that case there is no need for RF adjustment at all because there is no RF coupling.

[alfisti71]

The "bad" one is a Fotodiox. Actually, now, two of them.. identical problem. They seem to be milled with the big ring too thick. I gave up and hit it with sandpaper and I filed it down till the adapter ring screwed in to the same spot the "working" one did - seems to be OK now.

 

The "working" one looks old and has no markings other than "5cm". It could literally be 70 years old at this point.

[alfisti71]

p.s. neither adapter has screws on it