Rangefinder calibration on Canon P and 7s

<p>Hello. I have both the P and 7s and I've noticed when shooting at around 7 ft, both rangefinders are off (ugly focusing errors). They are "on" at infinity. Moreover, my Canon bottomloader (a IID1) serviced by Gerry @ Kindermann a few years back is spot-on both at 7 ft and infinity. This was so annoying that I got to the point of measuring the distance between the tripod-mounted camera and a Navy test focusing chart. I measured the film plane to target distance AFTER focusing using the same lens on all three cameras. (The bottom-loader showed the exact distance -- about 6'10" -- and the P and 7s showed about 7.25' [7'3"].)</p>

<p>I read up on how to calibrate the horizontal and vertical rangefinder on both the P and 7s at infinity -- seems straightforward providing you have the correct tools -- but no mention is made of a second, close-focus calibration step. How is that performed?</p>

<p>Thanks.</p>

<p>I forgot to mention that both the 7s and P have been freshly CLA'd by a reputable organization frequently recommended on this forum.</p>

<p>That's a mysterious problem. I'm sure there are no close focus adjustments. The usual drill is to set the camera's RF infinity focus, then everything else will work right at all the distances, provided there are no camera issues. Maybe the little arm that rides against the lens is binding at close distances? For what it's worth, I had a P and it was one of the best focusing LTM cameras I ever owned at close distances. Nice cameras. </p>

<p>The infinity adjustment should be all you need, if done properly then after that any discrepancies would likely be to base length differences.</p>

<p>In my opinion, the numbers you gave aren't terrible. Being 0.3 of a foot between the three models falls well within reasonable tolerances.</p>

<p>What lens were you using? One of the caveats with Canon rangefinders is that some of the lenses made by Canon were too fast to be focused accurately by them (the 50 F0.95 for example). This is because these cameras (like all rangefinders) are usually off a little bit and the focus shift is seen with the shallow DOF lenses.</p>

<p>John and Steve: I discovered this problem when I got a new (for me) lens and was walking around a park seeing how it performed. I focused on some signs -- very close -- and when the film was developed, the letters on the sign were out of focus. Infinity was fine. That prompted the test, which them prompted a re-test using all three cameras. </p>

<p>The lens I tested with was Canon's 80/1.5 ... one of my fastest lens chosen deliberately to highlight any potential focusing issues. I tested it on all F-stops to see how bad the calibration was off. I also tested it at different focusing distances. I also tested using the Canon 135/F3.5 which showed the same issue at close distance, wide open.</p><div></div>

<p>Maybe you're seeing focus shift too? Where the lens focus point "shifts" slightly depending on it's optical design, aperture used, and focus distance? </p>

<p>Yes, there is an adjustment for this. The roller on the end of the rangefinder arm is mounted on an eccentric that can be rotated with the correct very thin open-end wrench. It changes the effective length of the rangefinder arm. This adjusts the "slope" or "rate" of the rangefinder function.<br>

To quite the Canon 7 service manual (which can be found online):<br>

3. When the double-image aligns at infinity but has a deviation at close distances<br>

Insert tool T06A-C151-747A or T06A-C151-747B between Focusing Roller Lever C9301 and Roller C0476 and turn the eccentric ring of C9301. Next, attach the lens and adjust the horizontal image. Repeat this operation until an accurate image is obtained.<br>

However, you should send it back to whoever did it, and have them make it right. You paid for repairs, they should make it right. Even Gerry, Don, and Sherry make mistakes, and will correct them, and should not make you wait in their work queue to do so.<br>

There's many things that have to be "right" for a Leica type rangefinder camera to focus accurately, to be fully "standardized". Correcting the rate of the rangefinder may be correcting for another error, like flange-film distance.</p>

<p><em><strong>John S</strong></em>, I couldn't have said it better myself...</p>

<p>John and Gus ... I had considered that but two things dissuaded me: (1) I asked if they performed the task and they said they did. If they forgot, OK. If they did and screwed it up, I don't want them touching my cameras again. BOTH cameras were done poorly. One camera ... maybe. Not two. (2) I had this service performed over six months ago. I never really noticed the issue until I was testing out the capabilities of that new (to me) Canon 85/F1.5, wide open. I'm not sure I want to get into the proverbial p*ssing contest over length of warranty on their work and why I didn't discover the issue before. So ... this becomes a lesson for me (test the heck out of my cameras or stick to one trusted service person) and an opportunity for me to figure out how to fine tune rangefinder calibration.</p>

<p>Now I need to order the tools to do this (on micro-tools site now). Hopefully I can get the tools and do this work during the holiday break, before "real" work gets too demanding.</p>

<p>Thanks everyone for your feedback and happy holidays!</p>

<p>You will need to make your own wrench. It needs to be thin. You may be able to use a thin hacksaw blade cut with a cutoff disk in a Moto-Tool. Or it may need to be even thinner than that. You may need some thinner stainless steel flat stock. You could use a feeler gauge set to figure out how thin it needs to be. With the inability to buy factory tools, you need to be nimble and make your own tools.<br>

But, don't be sure that the Canon 85/1.5 is correct either! It may be a mutt, with the optics from one lens, and the focusing mount from another. Focusing mounts are made with different cuts for the RF cam based on the actual focal length of the lens. Or one poorly seated lens element (from a prior interior cleaning repair) could put the lens off-focal-length. It's possible the lens is wrong, the P and 7s are correct, and the IID1 is wrong. (But not too likely.)<br>

A good way to double check is to use a 50mm lens (which doesn't have a separate cam), and see that the rangefinder agrees with the focusing scale.</p>

<p>John -- thanks for all the information. I had breakfast with a friend yesterday. He owns a fully-equipped metal working shop and has offered to fabricate a couple tools for me. He and I both looked for a tool, not a general-purpose spanner -- to fit the rotating adjustment on the deck of the 7s and didn't find one so he's using my camera to design a purpose-built tool to fit that (he's bored and looking for projects). The thin wrench is a problem as there is no template to design from, at least which he or I can locate. I don't suppose you have any specific information on what those tools (T06A-C151-747A or T06A-C151-747B) look like?<br>

<br>

As you suggest, I'll test the infinity calibration with another lens. It would be nice if it were that simple a problem ... a Christmas wish, perhaps?<br>

<br>

As always ... thank you!</p>

<p>It's just a very thin open-end wrench. Don't know the size. The roller is held in with a screw, take the screw and roller off and you should be able to measure across the flats with a vernier caliper. Not a high-torque application, shouldn't need hardened steel.<br>

<a href="http://www.pentax-manuals.com/manuals/service/canon%207%20repair.pdf">One source of the Canon 7 repair manual</a> (which is fully suitable for the rangefinder on the 7s).</p>

 

<p>For those of you still monitoring this thread, my friend Larry crafted for me this adjustment tool in his metal shop. This is for the vertical adjustment (which I now realize was off slightly). I'll give the vertical adjustment a shot and see if that helps.</p><div></div>

<p>Here's another shot of the tool, next to the camera. Nice to have a friend who has metal working skills and the motivation to screw around making the tool for me!</p><div></div>

<p>Looking at the depth of field tables for 7', it appears your two test lenses each have a depth of field wide open of about 1.5-6" or a near and far focus depth of 3/4" from optimum. As you stated in your post, to be off 5" at 7' is quite a bit. May I suggest the following:<br>

Although access to a 7' optical bench may not be possible, your friend may be able to help you construct a very accurate 2x6x8' wooden test target beam with markings exactly 7' from target to camera film plane. As the distance from the lens mount plate to the film plane is a known dimension, the 7' depth can be accurately determined by measuring off the lens mount and adding back the depth. Once both target and camera body film plane are level and 90 degrees to the beam both vertically and horizontally, with either lens set at 7' you'd be able to see how far off and how much alignment adjustment is needed on the rangefinder eccentric. Perhaps you'll be lucky and able to adjust while the camera remains clamped to the beam. Once the rangefinder's 7' focus is aligned both vertically and horizontally, you'll be able to check other focus points all the way back to the minimum focus depth of the lens and still be sure the 7' focus alignment remains in rangefinder focus. Wait for a clear night to do the infinity check on the moon or bright star. The real acid test will be whether the target film slide images are actually in focus at the selected distances. Using this method takes lens focal shift out of the adjustment as the focus accuracy is being determined solely by the lens's rangefinder cam rim to the camera rangefinder actuating arm as transmitted through the eccentric adjustment. I hope setting the 7' focus doesn't throw off infinity or close in focus accuracy. Best of luck however you go about this project.</p>

<p>Christopher ... it will take some time but your suggestion will be the next step. Thankfully, the manual John pointed out pretty much spells out the steps. It's a matter of getting some additional tools as well. Thank you!</p>

<p>Hi Carl,<br>

A company called Moody's makes a thin minature open end wrench set from 2.5mm larger in .5mm increments. They may have what you need.</p>