Question About Focusing J-11 on Canon/Leica

[nation_of_pomation]

I bought a Jupiter-11 recently, but before I could test it I encountered problems with my Zork-4K and -6 and since there's no way I'd shoot anything wider than 50mm on my FED-5B, I tested it on my Canon P. Is there any reason why the rounded rangefinder cam might have made it focus incorrectly? All my closer subjects are out of focus, and I didn't have that problem with the Canon 135mm f3.5 lens with a tab instead of a collar. I had the same problem with close focusing the other way around when I tried the Canon 135mm on the Zorki-4K before I messed it up and it was clearly the tab not engaging the rangefinder cam exactly the way it was intended to after it was explained to me by a patient RFF user. I've also shot a Jupiter-9 on the Canon P with fair success, but it could just be a less noticeable focus error since it's a wider lens. I'm also not infallible, so it could have been user error, but I feel like it wouldn't be every single close subject had it been all me. I got this lens from Fedka, so I'm pretty confident there's nothing wrong with the lens itself. Thoughts?

 

[wolves3012]

FSU cameras use a slightly different working distance from the Leica standard, this is well documented and much argued about. However, if your J-11 is spot-on for its designed distance it is probably about the worst-case scenario to be using it close-up and wide open, in terms of focus errors. You could try using it on an FSU body to confirm, if the problem goes away then you have your answer.

 

[nation_of_pomation]

I just bought some 12 exposure rolls, so I think I'll use one to compare the Canon 135mm f3.5 to the J-11, and if it turns out it doesn't focus properly, I will shelve the lenses until I get my long-rangefinder-base bodies repaired and just stick with nothing FSU longer than 50mm until then. I guess I was just hoping that the slight registration difference wouldn't matter too much, but maybe it really does exist after all.