Canon LTM Different lenses, different snap, same aerial

[alexnotalex]

I'm confused. I have a Canon P rangefinder (love it) and two 50 lenses - an uncoated Summar from 95 and an Industar-61 from the seventies. I'm extatic with the results I get from both - but I just noticed one strange thing.When I focus on distant objects, I get different results from "infinity"

I've been practising with a distant aerial. I carefully adjusted my rangefinder so that the Industar snaps at infinity. When i mount the Summar and focus on the same thing, it snaps just before the infinity lock, at 50ft... when I set the lens to infinity, it's beyond the snap and it looks out of focus. I'm now not entirely sure I can trust the snap with either...

Do I have a problem with the camera, the lenses, or is this a normal feature I should just stop worrying about?

Many thanks for any advice,

Alex

 

[alexnotalex]

I've been testing more at short distances - I adjusted the Summar so it snaps at infinity, and at 4 feet - perfect and consistent. Now the industar is slightly out at infinity, and at short distances - the snap is at 1.3m when the tape measure shows 1.2.

Any thoughts folks? Been seeing many readers but not many comments...

Thanks

 

[xwhatsit]

The Soviet 39mm system used a slightly different lens register, didn't it? There's lots of threads here about people shimming their Jupiters and Industars to work with Leica and Canon bodies. That would cause it, wouldn't it?

 

[alexnotalex]

Thanks very much for the tip, I'll have a look at that. My lovely Industar might end up on ebay....

 

[ruby.monkey]

Thanks very much for the tip, I'll have a look at that. My lovely Industar might end up on ebay....

Is this actually causing you problems? Ruining shots? Because if not then there's no reason to get rid of the lens.

An example - I have a 50mm f/1.5 Jupiter-3 that has been adjusted for accurate close focus on a Leica. This means that infinity focus doesn't match my Leicas' rangefinders. Despite this, all shots at all distances are more than sharp enough, even wide open - the increasing depth of field at longer ranges compensates for any mismatch between lens and body.

 

[alexnotalex]

Thanks for your comments and advice. The results are technically fine. Now I understand whats going on I can stop down and stop worrying. I do most of my film photos outside in the daytime so won't usually be wider than 5.6

Thanks!

some pleasing test shots here.
http://www.flickr.com/photos/48737663@N02/4694444144/

http://www.flickr.com/photos/48737663@N02/4760472366/

 

[Sonnar Brian]

The Summar is made to the Leica standard focal length and agrees with the Canon. The Industar is made to the Zeiss standard. The focal length is longer than the Summar. You can get the Canon to work perfectly with the Industar at one exact distance, but can make it work with the Summar at all distances.

This is the compatibilityproblem between the two systems.

Here is how I adjusted mine for the Leica:

http://www.rangefinderforum.com/forums/showthread.php?t=91163

 

[alexnotalex]

Wow, amazing work Brian, you really know your stuff. All the posts have helped me understand the issue,
Many thanks!