Canonet QL17 GIII - adjust lens to infinity

[Spyderman]

Hi,

As I was reading some posts in the Russian RF section about lens collimation using 2 cameras, I decided to test my lenses whether they focus properly. First I tested my FSU LTM lenses Industar 61 and Jupiter 8 - both were fine. But when I tried it with my Canonet I was shocked!

The canonet's infinity was at about 10m on the scale! 😕

The solution was quite easy: (just in case someone would want to do the same)
- remove the bottom cover
- set lens to minimum focus
- loosen 2 screws (near the resistance-path for flashmatic function) holding the focusing lever together with the focusing helical (one with flat head for philips screwdriver + one sunken set-screw for flat screwdriver)
- rotate the the focusing lever as needed to have the lens at infinity when the scale is at infinity
- retighten all screws and put on the bottom cover
- recalibrate rangefinder (there's a hole in the hot-shoe..)
😎

Funny thing is that I used to shoot a lot with the camera, and the sharpness seemed OK to me. I guess the lens will be even sharper now! can't wait to take it out for a shoot...

 

[vicmortelmans]

I don't know the interior of the Canonet good enough to understand what exactly you did adjust, but isn't there a chance that you messed things up rather than adjusted them?

When adjusting my Zorki 4 focusing, I realised that for proper focusing you need three parameters to match: the distance read-out on the lens focusing ring, the image alignment in the viewfinder and the actual focus on the filmplane.

Taking them two-by-two, you need:

1. to match the rangefinder focus confirmation to the distance read-out on the lens focusing ring and
2. to match the rangefinder focus confirmation (two images overlapping in the viewfinder) to actual focus of the image in the film plane
(and if 1. and 2. are ok, you automatically match the distance read-out on the lens to the actual focus of the image in the film plane)

If you only do the first adjustment, you may end up with a rangefinder that aligns very nice on far distant objects when the focusing ring is set to infinity, but that does not focus this same object on the film plane!

Also, if the rangefinder aligns on a far distant object and the focusing ring shows 10m, that doesn't necessarily mean that the image will be out of focus!

Now practically, the first match is set by adjusting the rangefinder (typically on Zorki and equivalents). This is a purely mechanical match: the optics of the lens are not involved. The second match is set by adjusting the lens focusing offset. This is an optical match.

So bottom line: I hope that you've improved your camera performance, but since you say that you didn't see a problem before, I hope you didn't do the wrong adjustment!

Groeten,

Vic

 

[Spyderman]

I did this:
1.) Two camera collimation test. The other camera was a SLR with 200mm lens focused at infinity. I put a transparent tape with a marked "x" in the Canonet's film plane, and with the back open and the two cameras facingI checked when the x will be sharpest when looking through the SLR viewfinder (and through the 200mm lens and through the Canonet's lens with shutter open at B). The x was sharpest when the scale on Canonet's lens showed 10m.
2.) I adjusted what I wrote in the original thread. (so that the x would be sharpest when the scale is at infinity)
3.) I adjusted rangefinder for infinity using the scale on the lens.

Don't be afraid. I know what I'm doing 😎 at least most of the time 🙄


PS: I recommend the two camera collimation test to all of you, especially those of you who have compact rangefinders with non-interchangable lenses. With interchangable lenses you just have to check the film-plane to lens flange distance. on LTM RF it should be 28,8mm.