Canon LTM 50/1.2 Mounting 'Anomaly'

[jt991]

<p>Specifically aimed at users of this lens . . .<br>

I have a newly serviced one (serial number 546**) for my Canon 7, and when screwing it on to the camera it turns very smoothly and steadily until almost the very last turn, when a noticeable degree of resistance is suddenly felt and the final turns needs a little more effort. (No force necessary). There are no problems using it whatsoever...viz. smooth focussing over the full distance range, and it behaves exactly the same on a Leica lllf that I just bought.<br />Both cameras are in full working order, by the way.<br />The only other lens I have for both cameras is a 50mm Jupiter 8 which (to coin a phrase) screws all the way in unhesitatingly.<br>

Are other users of this lens familiar with this characteristic? Is it in fact normal ?</p>

[john_shriver]

<p>Someone had a similar problem elsewhere some months ago, and the problem apparently was that the lens mount on the camera was slightly bent due to bad shimming under it. The shimming is critical, as it's part of the calibration of the camera. If loosening the mounting screws on the mount a bit eliminates the binding, that's the problem. But you need a Leica/Canon professional to work on it, as the distance from the lens mount to the film plane is critical for accurate focusing.</p>

[james_elwing]

<p>Does it do the same if you wind focus out to closest distance before screwing in to body</p>

[jt991]

<p>I had always set the distance scale to the closest distance before screwing it in James, but latterly - after discussing the so called anomaly in another site's forum - no longer do so, as the general opinion there is to set the lens to infinity. Problem solved. Interestingly Leica's own Instructions for the use of Models c, f & g does not specifically advise on this point. </p>

[james_elwing]

<p>Don't get me wrong, James; I assume that having the lens locked at infinity is what Leitz would have advised us to do, and that's not normally a problem.<br>

It's just something I noticed happened with some of my own lenses, and winding it out seemed to eliminate the problem you describe.<br>

I always, however, wind out any TM 135, (Hektor/Elmar) because it has a limited RF cam, and the RF wheel on the camera would be moved on each revolution screwing it in.</p>

[mukul_dube]

<p>John, the problem occurs on two bodies, so, if your hypothesis is correct, the mounts of both bodies must have the same defect. Around 1962 I was taught to set a lens to its closest focus before mounting it. The stated reason was minimal pressure on the R/F cam follower.</p>

[jt991]

<p>I have been perusing my reprint copy of the Leica Instructions for use of the Models c,f and g more thoroughly (see my post above dated March 23 which was incorrect), and in the section covering the g series find the following instruction : "Lenses with infinity lock should be locked at infinity for changing".<br>

I very recently obtained my copy of the Leica Instructions referred to from ABE Books, whose URL is<br>

http://www.abebooks.co.uk/servlet/SearchResults?kn=Leica+Instructions&n=100121503&sts=t </p>

 

[mukul_dube]

<p>From the Canon 7 manual: "When mounting or dismounting a lens of 85mm or greater focal length, be sure to set it at the nearest footage setting" (see James E. above).<br />A locked infinity catch is convenient to rotate the lens to mount or remove it. With the lens at closest focus, the infinity catch can only be used for mounting the lens.</p>

[mukul_dube]

<p>Sorry, that should have been<br>

<em>With a locked infinity catch the focussing tab is convenient to rotate the lens to mount or remove it. With the lens at closest focus, the focussing tab helps while mounting the lens.</em><br>

It was 5 in the morning and the coffee was not ready.</p>