Baffling Canon 7 focussing problem

[jt991]

<p>Negatives of the second film put through my allegedly "fully working, Exc+ six months guaranteed" Canon 7 reveal that all the frames taken with the similarly described freshly serviced Canon 50mm f1.2 are unfocused, and the remainder - with a similar quality (but not recently serviced) Canon 135mm f3.5 are in focus. As I have been a keen amateur for 50 years, used RF and a SLR Leicas, SLR Nikons, etc with moderate to great success, this anomaly has completely baffled me. The only cause I can imagine is that the rangefinder actuating arm and or its roller are out of line.. though not by enough when the cam of the 135 comes by. And before any one asks, yes I turn the 135's distance scale to 1m before I put the lens on.<br>

ps All the Negatives from the first film (taken with the 50mm lens) are out of focus, which is why I tried another film just after the 135 lens was bought.</p>

[mukul_dube]

<p>Sounds like a problem with the 50/1.2.</p>

[SCL]

<p>Put the camera on a tripod, attach a shutter release cable which you can lock open, set the shutter to Bulb, open the back and release the shutter. Put a piece of fine ground glass or even an old matte focusing screen (if you have it) against the film rails. Attach your 135 lens and focus on an object using the rangefinder/viewfinder. Check the ground glass with a loupe....everything should be in focus, just as your film showed....if not you may need to slightly shift the ground glass until it is in focus. Now substitute your new Canon 50 and repeat the process. If you have another 50 lens try that also. If neither 50 lens focuses...the cam may need adjustment. If one lens focuses and the other doesn't, then the issue is with the lens itself...the lens may need to be collimated, or perhaps it was disassembled and reassembled with the helicals on the wrong starting point. I had a lens like that and sent it to Youxin Ye and now it works perfectly well.</p>

[jt991]

<p> Thank you Stephen for your contribution, particularly for describing the probable causes.<br>

Although the camera and lens were bought together, as I have a LTM Jupiter 50mm the camera body was sent at my request directly to me whilst the Canon lens was sent separately to be serviced. (I preferred to use the camera straightaway, rather than wait for up to four weeks for the lens) Therefore I (still) assume that presence of the camera isn't necessary for collimation as well as disassembly & reassembly of the lens. <br>

To cut along story short, the lens has gone back (together with the camera this time), to the same repairer; well known and recommended, whose name I'll withhold for now as every other time I have dealt with them turned out satisfactorily. I will post again in this thread to report the outcome.</p>

 

[john_shriver]

<p>There's six things that have to be right to make an LTM interchangeable lens rangefinder camera focus accurately:</p>

<ol>

<li>Lens mount must be 28.80 mm from the film plane, and parallel to it.</li>

<li>Rangefinder must align at infinity when the roller is 7mm in from the lens mount.</li>

<li>Lens must be properly collimated so it is focused at infinity (at infinity setting) with its mount 28.80 mm from the film.</li>

<li>The rate of the rangefinder action in the camera must be correct, so that when a 51.8mm focal-length lens is focused at 1 meter, the rangefinder indicates 1 meter. (This is essentially controlled by the length of the rangefinder coupling arm.)</li>

<li>The rangefinder coupling cam on the lens must project exactly 7mm from the mounting face when the lens is at infinity focus.</li>

<li>The rangefinder coupling cam on the lens must move away from the camera as you focus closer at the correct rate for a 51.8mm lens, no matter what the actual focal length of the lens. This is why any lens but a 50mm lens has double-helicals (wide angle) or a tracking cam (long lens).</li>

</ol>

<p>This is not something you can do at home without a lot of specialized jigs and test devices. <br /> Why is the Canon 50/1.2 giving trouble? Well, partly, it's got shallower depth-of-focus than the 135/3.5. So it's possible it just exposes an error in the camera. On the other hand, someone may have taken the lens block out of the focusing barrel (possibly to clean the rather common occurrence of oily haze inside this lens) and forgot to put back the selected shim that selects for infinity focus. <br /> Or someone may have taken the focusing mount from one lens, and the lens block from another lens, and made a "Frankenlens" out of it. (Making the "best looking" assembly from two lenses.) Problem is that at least Leica made focusing mounts for lens blocks of different focal lengths, and then matched it with a lens block that had that focal length. (This happens because lens grinding has lots of control of the radius of curvature of a lens element, but less control of the thickness of an element.) Leica marked their helicals to indicate their focal length, at first in code, later explicitly. You'll also see serial numbers penciled into focusing helicals, which should match the serial number of the lens.<br /> Or someone may have taken the focusing helical apart, and put it together on the wrong start of the threads. <br /> You need a professional with the right tools to solve these problems.</p>

[Brian1664876441]

Does the distance scale and RF of the camera agree? If the RF pickup is not engaging the RF cam correctly, the distance

scale will be way off. If the two agree at infinity, the problem is either the Shim of the lens is not setting the correct

standoff, or the elements of the lens are not in the correct position.

[Aoresteen]

<p>I have a Canon 50mm f/1.2 (my 2nd copy) and they MUST be properly adjusted or they will be out of focus. I sold my first copy thinking it was a soft lens but what it needed was a proper adjustment.</p>

<p>I sent my M3 and the 50mm f/1.2 to my service provider to ensure BOTH were properly adjusted. Now that you have done the same I'm sure things will be sorted out. Usually the 135mm is the hardest lens to focus on a Leica so that tells me that your body was in spec and the 50mm f/1.2 was in need of adjustment. If the 135mm becomes out of focus then there is something amiss in the camera.</p>

[michael_darnton2]

<p>You don't specify the most important thing here: HOW are they out? Consistently focusing closer, farther? At what lens opening? If the misfocus is not consistently one way or the other at the same opening (!), the problem is you, not the camera. A 50/1.2 lens can be really difficult to focus, and you also need to know how to deal with a lens' focus creep when it's stopped down--with most older fast lenses the point of focus will move backwards as you stop down, so being spot on wide open can turn into an inch or three back focused two stops down, or an inch or two front focus wide open can be perfect from f2-2.8 down from there.</p>

<p>I've had quite a few Canon RF lenses over the years. My impression has been that Canon's calibration of them regarding the rangefinder was, uh, loose, to put it politely. They've been universally great lenses, but mostly a bit off with the rangefinder. Nothing that can't be fixed, though. IF your camera's rangefinder is properly adjusted, the minimum you should ask is that all lenses click exactly in to infinity on an object that's a couple of miles away. With Canon lenses, that's usually the problem, and it can be easy to fix. In my experience, once you get that going right all of the closer distances fall into line fine.</p>

<p> </p>

[james_elwing]

<p>Be fair. Canon RF lenses will be over 50 years old, therefore probably have been through a few hands. Bit hard to blame Canon for accurate adjustment. </p>

[jt991]

<p>OP's Update following todays conversation with the repairer:<br>

(a) There is nothing wrong with the camera and (b) he is evidently going to have to disassemble the front of the lens to fix it because something “must have gone wrong” during the reassembly prior to it being forwarded on to me. . He concluded with a promise to email me tomorrow with another update, and I am hopeful that it may be back after three days. (Human error, sincere apology, prioritisation and customer goodwill are all part of this experience)<br>

</p>

[michael_darnton2]

<p>James E: That's funny, but I've been doing this long enough to have bought Canon RF lenses new, and can vouch for their quality "back then", too. :-)</p>

[jt991]

<p>The repairer has told me that the "something" that was wrong with this lens, is that instead of the point of focus being at the film plane, it is in effect an inch (25cm) behind the film plane.<br>

I didn't fully grasp the technicalities of the proposed remedy, which involves the cannibalisation of another Canon 50mm 1.2 lens for (was it one ?) of its element to be transplanted. <br>

So I probably won't need the Jupiter 8 I bought for a Fed some time back, as shouldn't be very long before the Canon lens comes back home.</p>

[glen_h]

<p>I can certainly see that the position is off, but I don't think it can be that far off.</p>

<p>And 25cm is closer to 10 inches. </p>

[jt991]

<p>Thanks for pointing out my glaring typo error Glen. 25mm is the right one.<br>

How can you see that the position is off ? That photo of the Jeep is 15 years old, and I haven't uploaded any of the out-of -focus images taken with the Canon Lens. All the affected images are so far out of focus, its impossible to tell what the subjects were without my notes.</p>