Sonnar 50mm 1:1,5 in a Leica Screw mount

[vinton]

Dear all,

Currently I bought a Sonnar lens new old stock on the eveilbay. It is like new but the problem is it is in a black non-focusing Leica screw mount barrel. I really want to remove the lens elements from the original barrel and put the lens elements in a Contax barrel or even a J-3 . The problem is I couldn't find a way to remove it. There is no screw on the barrel and ...

Does anyone know how to remove it without disambling the lens elements.

 

[vinton]

http://www.rangefinderforum.com/photopost/showphoto.php?photo=162818

 

[Sonnar Brian]

This looks like it was used for an enlarger. I bought a 5cm F2 lens like this. I ended up transplanting the optics into a spare fixture piece by piece.

The alternative was to cut the fixture that you see, get the optical fixture out that way. It looks like the Zeiss fixture was cemented on mine.

Best guess: take out the rear module using a spanner. That may help. If it does not, you are probably dealing with cement.

This is a post-war Zeiss lens, and the optics will not fit into a J-3 mount. You need a "dead" post war lens of the correct type. There are two versions of the post-war West German Zeiss lens that I have seen, the construction of the fixtures is different.

 

[john neal]

Brian,

I have been looking at my 1937 Sonnar f1.5 - this was OK on my MP, but after a trip in the mail, failed to work on another member's M3. Having decided to strip it right down to remove oil on the blades, and some haze on the inner surfaces, I reassembled an collimated using the SLR "face to face" method - looking for a good infinity.

Well, first test shots are now processed and I'm somewhat confused. Here's a selection:-

shot at f4 or 5.6 - as close as I could go ~ 1m. Not too bad, given it is hand held on the M3 (Acros 100)

but then:-

again, about f5.6, focus on the "bright" leaf shape - 2nd from left, but where has focus fallen? Again:-

f4 again - I'm sure I focussed on the closest vertical....

f2.8, and I know I was spot on the lettering on the organists's shirt with the RF patch. Finally:-

f1.5 - focus on the closest leaf, but sharp on the trunk? OK, the leaf was blowing, but this is 1/1000.

Sonnar shift, but how far???

Any ideas - this suggests that the optics need to come out of the mount some, but is that consistent across all these shots?

 

[Sonnar Brian]

Okay, looks like you have a back-focus problem. I never trusted the real way to collimate a lens made to the Zeiss standard for a camera made to the Leica standard. The Zeiss lens can be set for a sweet spot to agree with the Leica RF, a mid-point is best. Pick somewhere between 3m and 5m, shim the lens to agree with the RF at that point. You want close-focus to be just in focus at F1.5, and set to F2.8 for infinity. If you optimize the lens for F1.5 at infinity, it will back-focus everywhere else.

The alternative is to polish the optical fixture down and move the rear module in closer. You need to take it down 0.8mm in focal length.

 

[john neal]

Thanks Brian, I will have to work out a way to confirm focus (I don't have your wonderful device - last one I saw at MW Classic was £150!!). I think I will pass on trying to change the focal length, so it could be I will have to find a focus screen to use on the M3 with the back door off.

I had spotted that 5m seems to be the sweet spot for this lens - similar to my f1.4 Canon, just couldn't get a way to confirm focus at that distance.

Does the f1.5 differ so much from the f2? I have used this method for both f2 Sonnar and J8 lenses before, with great success.

 

[Sonnar Brian]

Some lenses vary in focal length: the closer the lens is to the Leica standard, the better it works. DOF at F2 is much greater than F1.5.

 

[john neal]

Thanks Brian - didn't realise the difference was that big though.

I have found a focus screen, just need to jury rig it to the back of the M3 when I get some time 😉

 

[john neal]

revisited....

revisited....

Ok, so I spent a little time with a focus screen and loupe setting the Sonar so it showed good focus between 3 - 5 meters. This actually turned out to be exactly one pitch on the optic thread from where I was last time (further out of the mount) 🙂

So, here are the latest results, shot on Ektar 100 at the end of a roll that has been hanging around for a while. Low res scans from the minilab - won't be using them again, slow, expensive and they managed to scratch the negs:-

f4 - focus on the bottle cap

f5.6 - focus on the Y shapes below the top rail

very similar shot from the Summitar - same film etc.

f4 again (too bright for anything larger!)

finally - f2.8 at infinity:-

I think this is about close enough - I also ran some v boring B&W shots around the garden using a bigger 'ole - close up is now spot on and anything over 5m just needs one stop to bring focus back to acceptable.

Brian, thanks again for the help and encouragement - I think this one's a keeper 😀