Pre-war Carl Zeiss Jena 5cm F1.5 and Russian LTM J-3 Swap

Brian · Joined: 10 May 2008 Posts: 83 Location: Virginia, US

It was rainy, my daughter had homework, and the CZJ Sonnar was slightly off in it's Contax Mount. And I do not think Zeiss made pre-war CZJ 5cm F1.5 Sonnars in LTM. This one is from 1935, one of the early ones that stops down to F11.

So, take the set screw from the back of the Contax mount and unscrew the beautiful brass optics module. Take off the shims, take of the variable stand-off ring, replace it with the stand-off ring from the J-3 after polishing it down about 0.5mm.

I have a Through-The-Lens viewer for LTM lenses. It is indispensible for these projects. I use a Canon IIf to get the distance to a lamp that I have set at 5m. Then, put the lens and shim it until the actual focus agrees.

Put on a camera and test with film. This is a Leica III made in 1936.

Brian · Joined: 10 May 2008 Posts: 83 Location: Virginia, US

So now what to do with the left-over parts? The J-3 optics module had some dust and marks on the internal surfaces. Some of these lenses are "serviced" and I've seen thumb-prints on the inner elements where they were pushed back into place. The rear module was in tight, so I pulled out the front optics, cleaned, and re-assembled.

The J-3 is shorter than the Zeiss lens. The F-Stop marking Vanished under that great Chrome Finish.

So the Contax Mount needed to be polished, a metal file and sand-paper.

Shim the optics module, requires use of the collimator and a Nikon/Contax mount to LTM adapter.

Lens collimated and in the mount, F-Stop lines up.

Shot of the lens and LTM adapter on the TTL Viewer.

And a test for the Nikon S3. I aimed the "sweet-Spot" for the close-up focus for the Nikon. Sometimes I hit it, sometimes not! If not, onto the Contax it will go.