canon 50mm f1.2 leica thread mount question

momosgarage · 08-04-2005

I just aquired a 50mm f1.2 leica thread mount lens, but I don't have anything to use it with. I have been trying to get a canon VT and some other less expensive thread leica mount cameras, but it appears it could take some time to get a good deal and then get it repaired. So I have decided to give a russian rangefinder a "try", but just as a temporary solution so I can at least use the lens.

I know that russian rangefinders have issues with lens compatibility and focusing distance. So I would like to know of the numerous models which one should I get to use with this lens? Which Zorki or FED models will give me the least amount of problems?

back alley · 08-04-2005

what's your budget for a canon ltm camera?

joe

momosgarage · 08-04-2005

I want to get a really beat up or broken VT, l-1, vit or VI-L for around $100 USD or less. I would then be willing to pay to get it up and running (I have a friend in the repair buisness, so I am not worried about this stage at all) Its not the money really, its the time involved in the whole process. The search should easliy eat up a couple of months alone. What about a russian FED or Zorki recommendation?

mac_wt · 08-04-2005

Watch out, the Canon f1.2 doesn't fit all russian cameras. Its diameter is too big. On the Fed 4 and 5 the covers of the viewfinder/rangefinder are a problem and on the Fed 1/Zorki 1 it obscures the viewvinder and rangefinder allmost completely. The Zorki 5/6 and the Fed 2 seem to be usable. They also have the longest rangefinder base.

Wim

ChrisN · 08-04-2005

Is the 50/1.2 much bigger in diameter than the 50/1.8? I can try my 50/1.8 on my Mir (Zorki 4) tonight and let you know how it fits. I'm pretty sure it would be ok, at least with that camera.

Roger Hicks · 08-04-2005

MUCH bigger.

But my 50/1.2 fits fine on my Zorkii 4K without obscuring the RF and appears to give the same rangefinder focus as the Jupiter. I've never used that combination, though, because I have other, better cameras.

Cheers,

Roger

ChrisN · 08-04-2005

Well, here's the 50/1.8 on the Mir. The 1.2 could be substantially bigger, as Roger indicated, but still be quite usable.

Edited to add: Just to be sure, you'd better to send it to me for a 1-month trial.

rover · 08-05-2005

I bet the 50/1.2 is twice the diameter of the 50/1.8.

rover · 08-05-2005

The 1.2 is on the camera and 1.8 is just below it.

ChrisN · 08-05-2005

Chris is right for cameras just at the moment, thanks Brian - it's momosgarage who's looking for a camera to suit his lens!

Brian - what is the dimension you have quoted below? (52.3mm Contax standard, as opposed to the 51.6mm Leica standard). I was thinking this was the register distance (is that the term?) from the mounting flange to the film backing plate, but that measures pretty close to 29mm.

I guess your point, though, is that there may be a difference between Russian and Canon in the calibration of the focus scale. Good point. I wasn't thinking about that, only the problem of clearance around the lens to give line-of-sight for the rangefinder and viewfinder. On that aspect, the dimensions for centre-of-viewfinder to centre-of-lens and centre-of-rangefinder-window to centre-of lens are about the same on the P and the Mir (within 1 mm) so I'm guessing that if I put a 1.2 onto the Mir, I'd still be able to focus and frame the picture. As you have pointed out, whether you could get the subject in correct focus at 1m, wide open, is a very different question.

Chris

rover · 08-05-2005

Speaking of the Canon 50/1.2.

http://www.photo.net/bboard/q-and-a-...?msg_id=00D79v

dreilly · 08-05-2005

Would that fit on a Leica CL?

ChrisN · 08-05-2005

GAS? Me? Not for the rest of this month, anyway!

You lost me! Just when I felt I was starting to get a grip on how this all works. I thought the reference to a focal length as "normal" (ie giving a normal perspective in relation to what the human eye sees) is related to the diagonal measurement of the negative, about 43mm for a 35mm negative. Any lens about that focal length can be thought of as a "normal" lens and most makers have interpreted that as about 50mm. Does the 52.3mm Contax standard and the 51.6mm Leica standard refer to this? I don't see how those numbers relate to the critical dimensions that determine whether the image will be in sharp focus at the film plane.

Tell me if I've got this right, please. This is long-winded but it’s the only way I know to check my understanding, so forgive me. Sorry if I sound like a PITA.

The LTM lens/body system relies on consistent dimensional relationships for focussing accurancy, between infinity and minimum focusing distance, across different lenses and different bodies.

The critical bits are that the lens elements have to be held a certain distance from the film plane, and the scale markings on the lens focusing sleeve should accurately reflect the distance to the object in focus, at all points between minimum and infinity.

For convenience, the rangefinder mechanism, with its cam and mirrors, relays a graphic representation of that information to me. So there's two indicators that the lens should be/ought to be in focus - the distance scale markings on the lens itself, and the overlapping images in the camera viewfinder. When all is working properly these two agree, and also coincide with sharp focus at the film plane, for that distance.

Now lets mate the lens up to the body. The lens flange is the flat surface where the lens meets the body. Leica set the lens flange-to-film plane distance (lens register) at 28.8mm, and all LTM lenses and bodies should follow this standard.

Lens designers, knowing that the mounting flange for the lens body will be 28.8mm from the film, know where to put the lens elements to achieve sharp focus at both ends of the focusing distance range. And this 28.8mm dimension also determines where they have to position the sleeve that moves the rangefinder cam in the camera body that relays the focus distance to me as overlapping images. That is the other part of the LTM standard – the correct distance of the rangefinder cam from the film plane. Because that’s relative to the mounting flange we can also measure it from the film plane.

Now I’ve just measured a modern CV LTM lens: at infinity on the lens focusing scale, the sleeve that rides the rangefinder cam is 12.5mm proud of the lens mounting flange (ie it sits deeper inside the camera, where it contacts the cam). I get the same measurement for the Canon 50/1.8. So the sleeve will be (28.8 minus 12.5 =) 16.3mm from the film plane when the lens is set at infinity. I hope that’s where my cam lies, and that the rest of the rangefinder mechanism lines up the overlapping images at that point. (I can’t measure it at the moment because both my LTM cameras have film in them.) With the lens focusing scale set at 1 meter, the sleeve is 4.6mm proud of the mounting flange, so the sleeve and the cam where it touches, should be (28.8mm – 4.6mm =) 24.2mm from the film plane. The full travel of the rangefinder cam, and the sleeve in the lens that pushes the cam, should be 7.9mm. When all these dimensions are held accurately and consistently by the makers of both the camera bodies and the lenses, and the rangefinder mechanism that moves the prisms are correctly adjusted, it should all work together.

How did I do?

If I’ve got that straight, the issue for momosgarage is that he wants a camera that will let him use his Canon 50/1.2. His Canon lens is built accurately for the Leica 28.8mm flange-to-film plane standard, so that’s what he needs. The problem is that some FSU LTM bodies are not built accurately to the 28.8mm lens register standard. He also needs enough clearance of the viewfinder and rangefinder windows to be able to see around that big chunk of lens.

Hey momosgarage, just buy a Canon and be done with it!

Chris

Frasergjb · 08-05-2005

51.6mm is the actual focal length for a "Leica Standard" normal lens, ie 50mm. 52.3mm is the actual focal length for a Contax standard "50mm" lens. The RF mechanism is calibrated for the normal lens (Cam Movement) and all the other lenses work to that standard. So a 135mm lens on a Leica uses a cam to translate the focus to the 51.6mm mechanism and a Contax 135mm lens translates the motion to 52.3mm. That is why if you stick a Contax lens on a Nikon RF the focus will be off. At 36", the error is about 1" if you stick a Sonnar onto a Nikon RF.

====

I am not sure that I understand what you are getting at. What does a difference in the actual focal length of a normal lens has to do with it? In other words, if you had a true 50mm focal length Contax lens, and a true 50mm leica lens, the reason that they wouldn't focus correctly when mounted on the "wrong" camera is that the cam movements/rates are different, and possibly the film register distance too, not because Leica's idea of what is a normal focal length differs from Contax's? This is why a nikon 50mm lens placed on a contax will focus correctly at infinity, but diverge during focussing to reduced distances, as you say. Both the Nikon and the Contax have the same "normal" definition and register distances don't they?

Sorry if I am missing your point!

ChrisN · 08-05-2005

That's odd. Camera Mounts sorted by Register lists both Nikon RF and Contax as having a 34.85mm register distance.

Frasergjb · 08-05-2005

Camera Mounts sorted by Register. lists both Nikon RF and Contax as having a 34.85mm register distance.

Frasergjb · 08-05-2005

Camera Mounts sorted by Register. lists both Nikon RF and Contax as having a 34.85mm register distance.

=====

I'm with ChrisN on this one. Nikon/Contax focus divergance is caused by different cam rates. You can adjust to choose where the focus is accurate, as you have done to bring it to 8ft, so that it diverges either side of 8ft.

An FSU LTM camera, within LTM tolerances, should be fine to focus a Canon f1.2 as the film registers should be be the same, even if the FSU camera usually has a 53mm normal lens. The question is whether the tolerances of the FSU camera are close enough!

harry01562 · 08-05-2005

Quote:

Originally Posted by rover

I bet the 50/1.2 is twice the diameter of the 50/1.8.

The 50/1.2 would probably work on one of the late Fed/Zorki models, but this is what it looks like on my Zorki 1.... it intrudes on almost 1/2 of the viewfinder.

Harry

Frasergjb · 08-05-2005

Right, now I understand what you are getting at! This is explained in some detail here, and I hadn't realised this before:

http://www.cameraquest.com/NRF-Contax.htm

So in this case Nikon/Contax cam rates are the SAME, but notional 50mm focal lengths are different. I must admit that I assumed that since the film registers are the same, the cam rates and/or helicals must be slightly different.

You learn something every day!

laptoprob · 08-05-2005

I have a 1,2 Canon lens and it is wonderful for (low light) portraits. I have used it on a Canon VI-T, Leica M2, CLE, Bessa T and Hexar. All works fine but the CLE is pushing the limits. The lens obscures part of the rangefinder but still workable.

Get a screwmount or M-adapter, forget the Russians because of the Contax helical errors.
This lens excels wide open, that's why it is special, that is why you could want it.

Rob.

momosgarage · 08-05-2005

Quote:

Get a screwmount or M-adapter, forget the Russians because of the Contax helical errors.

I have considered getting a bessa r2 or r3, minolta cl and cle. The price is right for all of these, but I personally like to hunt for what I need and I know how long that could take. I am not in any rush. The russian RF would just be a short term stopgap. I use ebay, so getting rid of it at a break even price wouldn't be much trouble at all. Thats why I do not consider getting one for a trial run as risky. Which model zorki or fed "can" work reasonably with the canon f1.2?

dreilly · 08-05-2005

If someone recommends a Zorki 4K as being able to work, I just got a body from Fedka in NY that' s in excellent shape, and I don't need it. I'd sell it to you a little less than what I paid. It comes with an ever-ready case that won't fit that 1.2. , however.

back alley · 08-05-2005

and i have a working perfectly canon screw mount body also!

canon on canon.

rover · 08-05-2005

I will pop the 50/1.2 on my Canon IV when I get home so we can see how that looks. I don't see it as being much better than the Zorki 1 though.

rover · 08-05-2005

OK, the 50/1.2 will mount on the Canon IV SB2, and it is usable, barely. The lens slightly protrudes into the RF window and you can see just the curve of the barrel in the RF patch in the viewfinder. It is there, but you can still focus the camera. You will just have to get used to seeing it there.