On the LTM -> M adaptors

[Finnkare]

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Have you had any bad examples of LTM-M adaptors? I am coming to the impression that they differ, but I'm not completely sure if they work the same.

 

For example, I have a couple of adaptors, which stop the infinity not up, but a bit off. With lenses, which couple to the rangefinder by a round shaped thingy this seems less crucial than with lenses, which couple with a straight thingy.

 

Both of these examples are, I think, non-Leitz and also non-Voigtländer. Have you been able to made any generalisations, which kind of adaptors work, which don't?

[wizard]

Even with the original Leitz adaptors you have to be lucky to have a given LTM lens line up perfectly up in an M-mount camera. And if you are lucky with one lens, that doesn't mean another lens will also lign up perfectly with that same adaptor (I have 7 or so original adaptors and a variety of LTM lenses, both Leica and Voigtländer, so I know what I am talking about).

 

Just don't worry about the usually small offset, it really doesn't matter.

 

As an aside, are those numbers you are quoting lens numbers or camera numbers? Makes quite a difference in age, you know .

 

Andy

[Finnkare]

Even with the original Leitz adaptors you have to be lucky to have a given LTM lens line up perfectly up in an M-mount camera. And if you are lucky with one lens, that doesn't mean another lens will also lign up perfectly with that same adaptor (I have 7 or so original adaptors and a variety of LTM lenses, both Leica and Voigtländer, so I know what I am talking about).

 

Hmm. So it's just good to have many adaptors, and it doesn't seem to really matter, which brand are they. Good to know, thanks.

 

Just don't worry about the usually small offset, it really doesn't matter.

 

But isn't the rangefinder cam (or what is that gizmo in the body called, which is moved by the lens to move the rangefinder mirrors) so narrow that if the moving part in the lens is narrow as well, they don't touch each other properly? I have a Hektor 135/4,5, whose infinity seems a bit "over". The offset with the adaptor is about 5 millimeters (.2 inch) to the direction of the shutter release.

 

The other LTM lens I have is a Canon 50/1.2, which is considerably offset, more than 1 centimeter (half an inch). The funny thing is that the infinity is absolutely spot on. The rangefinder is moved with a round shaped thing, not a straight one like in the Hektor.

 

As an aside, are those numbers you are quoting lens numbers or camera numbers? Makes quite a difference in age, you know .

 

Hmm, you're right. I'm either 26 or 51 . Maybe I'll put the other one in there too...

[doubice]

The offset from ‘TDC’ (or top dead center) varies with Leica thread lenses. Generally, lenses below 50mm will be offset by about 10mm; while telephoto lenses will have no offset at all. There are of course some exceptions but, I did say ‘generally’…..

 

The reason for the offset was that shorter focal length lenses’ distance scale would have been difficult to see when an accessory finder was inserted into the camera’s shoe. The accessory finders, particularly the long-nosed ones, extended over the front of the camera body and would have obstructed the focus index mark, had it been at TDC.Telephoto lenses of course had their distance scales further up front on the lens barrel so, the offset was not necessary.

 

If you do find a lens which is supposed to sit at TDC but does not (offset by just a few mm’s), this is due to wear on the lens mount. Such a tiny offset is negligible and has no influence on the focusing accuracy.

 

Best way to check if a lens is correctly oriented on the camera once mounted in the LTM to M adapter, is to set the camera at ‘B’, open the shutter and observe where the lens’ RF cam sits. You will find that in 100% cases all will be fine, no matter where the lens’ focus index mark is positioned.

 

I have never run into any accuracy problems with original Leitz or the Voigtländer adapters. Never tried the cheap ones available from China lately so, cannot comment on those.

 

All the best,

 

Jan

[Finnkare]

^ That's interesting, I have to look into this.

 

I forgot to mention that the offset on the Canon is on the other side compared to the Hektor. So the infinity points in the direction of the viewfinder.

[Guest liesevolvo]

Hi, Finnkare, never try one of those cheap adapters! In best case You only have to throw it away, in worst case You have a ruined camera or lens. I came out of it best case... Normally a used Leitz has the same price as a new Voigtlaender, there has been one V-Adapter for me with some trouble, company changed it very fast.

 

Best wishes from Cologne/Germany, Lenn

[gyoung]

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I have had trouble with the Komura one which came with the 2x converter I bought, it allowed the 135 Elmar to sag downwards (obviously!) if the lens ands body were not both supported, this pulled the rangefinder 'cam' on the converter forward and thus the focussing was well out, i.e. the focus point was well forward of the point focussed on. The Voigtlander adaptors performed much better but only the Leica one held the lens/converter combo tight up against the flange on the camera.

An extreme situation but indicative of manufacturing standards and materials I think.

 

Gerry

[doubice]

^ That's interesting, I have to look into this.

 

I forgot to mention that the offset on the Canon is on the other side compared to the Hektor. So the infinity points in the direction of the viewfinder.

 

On lenses which are supposed to have an offset focus index mark, the offset will always be to the left (when looking from the top of the camera. If your Hektor's index mark sits slightly to the right of TDC, that would indicate that it is either not screwed in tightly enough or, its mount has not been worn at all.

 

Again - as I mentioned above, nothing to worry about.

 

Best,

 

Jan

[doubice]

Hi, Finnkare, never try one of those cheap adapters! In best case You only have to throw it away, in worst case You have a ruined camera or lens. I came out of it best case... Normally a used Leitz has the same price as a new Voigtlaender, there has been one V-Adapter for me with some trouble, company changed it very fast.

 

Best wishes from Cologne/Germany, Lenn

 

Well, I would not go as far as to say that the cheap Chinesese adapter would ruin the camera or the lens. It will either fit or not and will either provide correct focus register or not. Given the precision of todays milling machines (even Chinese ones...), I doubt that there would be big issues.

 

Best,

 

Jan

[Finnkare]

Actually, I just learned from an older Canon 50/1.2 user that it is supposed to stay that way! He said it's designed in order to more easily see the scale also when taking vertical pictures... Funny.

[Irishimage]

One important point to remember regarding quality of any make of LTM m39/M Adaptor is the machined thickness of the flange.

 

This must measure 1.0mm exactly,otherwise the flange to film plane distance will not match the difference between Threadmount and M cameras,which is 1.0mm,and focusing of the lens will be affected.

 

If you have the means,measure this with a Micrometer or Vernier Caliper Gauge then this alone will confirm the quality/accuracy of the flange.

 

Noel

[giordano]

This must measure 1.0mm exactly,otherwise the flange to film plane distance will not match the difference between Threadmount and M cameras,which is 1.0mm,and focusing of the lens will be affected.

 

Variations in the thickness of the adapter actually don't affect the accuracy of rangefinder focusing of 50mm lenses.

[jaapv]

I'm afraid they do. The thickness and location are critical tolerances in the rangefinder mechanism. Some lenses do have an offset. The LTM Summarit 1.5/50 is mounted with TDC about 30 degrees to the left, for instance.

[wizard]

Variations in the thickness of the adapter actually don't affect the accuracy of rangefinder focusing of 50mm lenses.

 

That is equivalent to saying film to flange distance does not affect the accuracy of focusing. And we all know it does, don't we?

 

Andy

[giordano]

I'm afraid they do. The thickness and location are critical tolerances in the rangefinder mechanism. Some lenses do have an offset. The LTM Summarit 1.5/50 is mounted with TDC about 30 degrees to the left, for instance.

 

I was waiting for someone to fall for this. With every lens except a 50mm the thickness is critical, but the Leica rangefinder was designed so the movement of the roller in the body is identical to the focusing movement of a (nominally 50mm) standard lens. In that case alone, an error in the thickness of the adapter won't affect the accuracy of the rangefinder (though if the adapter is too thick you won't be able to focus on infinity, and if it's too thin you'll be able to focus beyond infinity).

 

In all other cases the thickness of the adapter affects the rangefinder focusing, though ten or fifteen microns either way isn't going to make much difference.

[wizard]

(though if the adapter is too thick you won't be able to focus on infinity, and if it's too thin you'll be able to focus beyond infinity).

 

My understanding of rangefinder focusing accuracy is such that if you either can't focus on infinity or can focus beyond infinity, then your rangefinder is NOT focusing accurately. Besides, if one of the above occurs, the rangefinder will be off in between, too.

 

Andy

[giordano]

My understanding of rangefinder focusing accuracy is such that if you either can't focus on infinity or can focus beyond infinity, then your rangefinder is NOT focusing accurately. Besides, if one of the above occurs, the rangefinder will be off in between, too.

 

I'll try again. Suppose the adapter is a little too thin. When the distance scale on the lens is set at infinity, the lens (assuming it's correctly adjusted in itself) will be "focused beyond infinity", and the rangefinder roller will be pushed beyond its infinity position - with the result that even the moon won't coincide in the rangefinder.

 

Then turn the focusing ring a little away from infinity. This lets the rangefinder roller reach its infinity position. The rangefinder images of the moon coincide - and the lens has been moved just far enough to reach its infinity position, so the picture of the moon is sharp too. This happens because and only because the movement of the rangefinder roller is designed to exactly match the focusing movement of the 50mm lens.

 

In this state, the distance scale on the lens shows incorrect distances but the rangefinder is bringing the lens to a correct focus even though the adapter is the wrong thickness.

 

If the adapter is too thick, it's similar, except that when the distance scale is at infinity the lens is focused at a closer distance - the same distance at which the images of an object coincide in the rangefinder.

 

Just another bit of knowledge that's useless until you need to use a duff adapter:D

[jaapv]

I was waiting for someone to fall for this. With every lens except a 50mm the thickness is critical, but the Leica rangefinder was designed so the movement of the roller in the body is identical to the focusing movement of a (nominally 50mm) standard lens. In that case alone, an error in the thickness of the adapter won't affect the accuracy of the rangefinder (though if the adapter is too thick you won't be able to focus on infinity, and if it's too thin you'll be able to focus beyond infinity).

 

In all other cases the thickness of the adapter affects the rangefinder focusing, though ten or fifteen microns either way isn't going to make much difference.

Ok, so you think it does not make a difference where the plane of focus is? Let's move the film a mm forward or backward then....

[doubice]

John is correct. The 50mm lens' in-out movement distance is identical to that of the rangefinder cam. So - no matter where the lens is positioned, if the RF image is in focus, so will be the lens (assuming that it is within specs of course).

 

John's nickname reminds me of Giordano Bruno - he preached a similar 'truthful heresy' and got burned at the stake for it. Hopefully John will not suffer similar fate....

 

Best,

 

Jan

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[luigi bertolotti]

Uhm... Giordano's point is subtle and not wrong : let's say... a certain tolerancing in adapter thickness (only in MINUS sign) , with a 50mm lens, is such that :

- The correspondance focus scale - actual focus is WRONG

- The RF focusing mechanism is correct, and the lens does focus to infinity (but its closest focusing distance is a bit longer than the nominal one)

 

With a tolerancing with PLUS sign you (in theory) cannot focus to infinty, but can focus correctly anyway to shoreter distances.

 

Of course, if one decides that "rangefinder is precise" means that user focuses right AND the corresponding distance in the focus scale is right, this is untrue with thickness tolerancing.