Canon P - Focus Testing

Grephenson · Jun 16, 2022

Hey everyone! I'd like to get your thoughts on what is potentially going on with my Canon P's focusing here. Here's the test I ran:

Calibrated the rangefinder at infinity
Setup on a tripod
Shooting a yard stick set at an angle
Focused on the 18" mark (red arrow)
Shot at all apertures

The results appear to not be good and the focus is at the about 24-25" mark instead of 18". Questions:

Do you agree where the focus is?
Was this a good way to test?
When calibrating at infinity, how far away should the object be? I've been doing it with something that is at least 100 yards away.

f4 / 1000 - https://i.ibb.co/71vbnfP/gs-sbfl-9.jpg
f5.6 / 500 - https://i.ibb.co/FHLt5n6/gs-sbfl-10.jpg
f8 / 250 - https://i.ibb.co/kQWfCyv/gs-sbfl-11.jpg
f11 / 125 - https://i.ibb.co/JyDYdhR/gs-sbfl-13.jpg
f16/ 60 - https://i.ibb.co/9gqhMHW/gs-sbfl-14.jpg
f22 / 30 - https://i.ibb.co/X3YgL5k/gs-sbfl-15.jpg

brbo · Jun 16, 2022

Focus looks to be further back, about 24-25" mark.

Grephenson · Jun 16, 2022

brbo said:
Focus looks to be further back, about 24-25" mark.

Dang. Now that I look at it on my retina screen, you're totally right. That makes sense too because the notepad is in focus and that was not at the 18' mark. I know for certain that this was calibrated perfectly at infinity. What could be causing this?

brbo · Jun 16, 2022

It was already said in your previous thread about this camera... do not assume rangefinder will be perfectly calibrated across the entire range just because it is calibrated at infinity.

Btw, how do you know for certain that it's calibrated perfectly at infinity? At such low resolution and with such grainy film/scans it's hard to see anything even at 1m distance where narrow dof is a big help.

Grephenson · Jun 16, 2022

brbo said:
It was already said in your previous thread about this camera... do not assume rangefinder will be perfectly calibrated across the entire range just because it is calibrated at infinity.

Btw, how do you know for certain that it's calibrated perfectly at infinity? At such low resolution and with such grainy film/scans it's hard to see anything even at 1m distance where narrow dof is a big help.

When calibrating at infinity, I used a piece of tape across the film plate and viewed the image projected on the tape with a digital microscope to view the focus at high resolution.

If I should not assume it will be calibrated across the entire range then what standard of calibration/focus should I even shoot for?

brbo · Jun 16, 2022

Well, if you are certain that infinity is ok and close focusing is not, then you need to adjust the "rate" or "slope"of the rangefinder.

If Canon P is anything like a Leica there will be two adjustments that you can do to get both infinity and close focus (and anything in between) correct. They are interdependent, you change one setting and you have to verify both infinity and close focus agreement.

Take a look here... This is for Leica and Canon P may or may not be similar.

Patrick Robert James · Jun 16, 2022

A piece of tape isn't going to be accurate. And you don't calibrate a rangefinder that way anyway. You need to calibrate it to a known lens. The film gate has nothing to do with it. My guess is you miscalibrated the infinity setting based on an erroneous reading at the film plane. Test the close focus against the numbers on the lens. Set the lens to one meter and see if the rangefinder agrees.

I've always calibrated cameras for infinity using the moon.

Grephenson · Jun 16, 2022

Patrick Robert James said:
A piece of tape isn't going to be accurate. And you don't calibrate a rangefinder that way anyway. You need to calibrate it to a known lens. The film gate has nothing to do with it. My guess is you miscalibrated the infinity setting based on an erroneous reading at the film plane. Test the close focus against the numbers on the lens. Set the lens to one meter and see if the rangefinder agrees.

I've always calibrated cameras for infinity using the moon.

Thank you for your response! When I set the lens to 1 meter and then focus on something 1 meter away do I measure that distance from the end of the lens or where the film gate would be?

Grephenson · Jun 16, 2022

I've been emailing with well known rangefinder repairer Youxin Ye of http://www.yyecamera.com and this is what he had to say:

"As a screw mount camera, the rangefinder cam is fixed, you can only adjust to infinity, all other distances supposed to be right after infinity is right."

btaylor · Jun 16, 2022

That’s good to know! And Youxin knows his stuff.
Again, getting back to the infinity adjustment it is critical that whatever you are using to check the film plane image is absolutely flat against the film rails. I use a piece of groundglass and a 6x loupe.

brbo · Jun 16, 2022

Grephenson said:
I've been emailing with well known rangefinder repairer Youxin Ye of http://www.yyecamera.com and this is what he had to say:

"As a screw mount camera, the rangefinder cam is fixed, you can only adjust to infinity, all other distances supposed to be right after infinity is right."

Funny that Canon 7 (screw mount camera) DOES have close focus adjustment.

(from Canon 7 repair manual)

Grephenson · Jun 16, 2022

Very interesting! I wonder if since the Canon 7 came after the P this was an improvement they made with this issue in mind.

reddesert · Jun 16, 2022

Several comments:

- I would start by aligning the rangefinder at infinity so that it agrees with the lens focusing scale at infinity. The film plane is nice in principle, but unless you are really careful a measurement there can be off. Ideally a groundglass and a loupe at the film plane will be accurate. But if it disagrees with the lens focusing scale then you have to think about whether your measuring system is accurate.

- Take a film exposure of an faraway object, focused at infinity, at a fairly wide f-stop, along with the close range yardstick tests. To confirm the infinity setting. (100 yards is just about far away enough if you use a 50mm lens, but even further would be better. If you use a longer lens the object should be further away.)

- The images of the yardstick that you posted are hard to read or see the true focused distance because overexposed. I don't know if this is the in-camera exposure or the scan, and you might be able to address it by darkening the jpegs.

__Brian · Jun 16, 2022

I use an exposed negative taped into place across the film rails, and a 15x Loupe that fits across the rails to hold the negative flat. That has worked for me in the past to shim lenses, before I got a specialized tool. Many people use SLR focusing screens held across the rails.

What lens are you using? Stopping down a lens will cause focus shift, usually towards infinity.

Patrick Robert James · Jun 16, 2022

Grephenson said:
Thank you for your response! When I set the lens to 1 meter and then focus on something 1 meter away do I measure that distance from the end of the lens or where the film gate would be?

Film. There usually is a mark on top of the camera near the shoe.

What lens are you using? Like Brian said, some lenses have a focus shift across their aperture range. Sonnars for example.

Start over again. Set the lens to infinity then calibrate the rangefinder on the moon or stars. Stars are great for vertical alignment. After you do that, if the lens doesn't focus where it should, the focus on the lens could be off, or the cam could be off, or the flange could be off. Better to check it with several lenses if you have them. If infinity is the same on all of them, then you should be good to go. Not all lenses are that accurate though, plus is possible someone messed with the flange over the years, removing a shim or something. That is why I mentioned a known good lens. If you are having issues after adjusting infinity, then check the lens with a ground glass on the film plane. If it doesn't hit infinity then there is either an issue with the lens or the flange on the camera. Frankly if it is off after you adjust for infinity then it is probably best to bite the bullet and send the camera and lens to someone who knows what they are doing.

btaylor · Jun 16, 2022

Patrick Robert James said:
Frankly if it is off after you adjust for infinity then it is probably best to bite the bullet and send the camera and lens to someone who knows what they are doing.

Oh yes, this is excellent advice. Youxin works on the Canon P (but not the 7’s, I checked). Very fair pricing, decent turnaround, I have always been happy with his work. Then you’ll have a camera that can take sharp photos!

Grephenson · Jun 16, 2022

@reddesert - Excellent thank you!

@__Brian - Oh good idea! I'm using a Voigtlander Color Skopar 35mm

@Patrick Robert James - Great, good to know. Thank you! Voigtlander Color Skopar 35mm. Here's the thing you won't believe I'm having the same issue with TWO different Canon P's and 4 different lenses. I know that's mind blowing and it probably means user error, but I've been very methodical about this whole thing. On roll 6 of test exposures now.

@btaylor - Youxin informed me he no longer works on any Canon Rangefinders made after the IVSB II.

brbo · Jun 17, 2022

Same problem with 2 different Canon P cameras and 4 different lenses? What are the odds?!

Were both cameras bought together from the same person? And lenses from another source?

Anyway, if you insist on doing the calibration yourself and you are certain that you have a good way of verifying the focus on film gate you'll need to also try with the adjustment of the eccentric rangefinder cam follower in combination with the horizontal adjustment that you've been doing so far.

Grephenson · Jun 17, 2022

@brbo yeah and the focus issues started right when I got them. I bought one from Japan of eBay, shot a roll, focus was off. Bought ANOTHER one in the classifieds forum on here, shot a roll, focus was off. I tried with different lenses each time. Thank you for that YouTube link!

guangong · Jun 17, 2022

I don’t see how taping film at gate will give accurate results. A friend, who worked at Leitz when on Canal St near Chinatown in his youth, corrected the rangefinder on my Nikon S2 at his desk using a pair of calipers. Although he explained the principles behind this technique to me at the time, I can’t repeat it. However, judging by pics, rangefinder is very accurate.

__Brian · Jun 18, 2022

I changed the shims behind the lens mount and calibrated the RF of one of my Nikon S2 bodies to accurately focus the Zeiss Opton 50/1.5.

Zeiss Opton 50mm F1.5, wide-open on the modified Nikon S2.

I used a piece of film taped to the gate and a loupe to calibrate.

It works because it is in the same location that the film is when taking a picture.

Patrick Robert James · Jun 18, 2022

Grephenson said:
@brbo yeah and the focus issues started right when I got them. I bought one from Japan of eBay, shot a roll, focus was off. Bought ANOTHER one in the classifieds forum on here, shot a roll, focus was off. I tried with different lenses each time. Thank you for that YouTube link!

Check to see if all the lenses register infinity on your rangefinders in the same position. If all four hit the same spot on the rangefinder then you can just concentrate on the camera rangefinders and don't have to worry about the lenses, probably...

reddesert · Jun 18, 2022

IMO, it is not unusual for an old rangefinder to need a small infinity adjustment. This is the OP's second thread on the subject, and (sorry OP), an issue is that the OP decided there was a focus problem and then started trying to adjust the rangefinders at a short distance without adjusting them for infinity focus first. So now, if both the bodies are out with all four lenses, it probably means they're both out, and not that there's something wrong with all the bodies and all the lenses. For ex, now we know one of the lenses is a Voigtlander 35mm, which I assume is the new-ish Voigtlander, not a 60 year old lens that someone might have fiddled with in the interim. It's probably fine.

If it were me I would put one of the lenses at the infinity setting, try to get the body rangefinder adjusted correctly at infinity, and then check that it's at infinity with the other lenses. Then I might check it at some closer distance (say 1-2m) checking that the lens focusing scale agrees with the tape measure distance (some small inaccuracy can be expected here). Then I might check it with a ground glass on the film rails (not tape for the accuracy we are trying to achieve), and then on film. But it's not possible to fiddle with the close settings without getting the RF adjusted correctly at infinity first. You'll just be chasing your tail around a series of tweaks, like trying to level a table by sawing an inch off each leg at a time.

gone · Jun 18, 2022

If infinity focus is correct then everything else should be fine. I use anything 70-100 feet for that, the moon is not really required.

If you're still having focus problems even w/ infinity set properly (camera was on a tripod or something stable, GG on the film rails, you used a loupe or a camera lens as a loupe), then something else is wrong. Sticking rangefinder, misaligned rangefinder, the lens is really the issue, rangefinder's cam is bent or otherwise misaligned, etc.

Canon P - Focus Testing

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