Repairing a Carl Zeiss Jena Biotar 58mm f/2 Lens

The Carl Zeiss Jena Biotar 58mm f/2 lens is a legendary lens. It consists of 6 elements in 4 groups and it was produced from the late 1930's to the early 1960's (before it was superseded by the equally legendary Pancolar 50mm f/1.8). The Biotar is famous for its swirly bokeh. After WWII, it was cloned in Russia under the name "Helios 44-2" which is now one of the most famous vintage lenses.

 

There are a few different versions of the Biotar with different aperture mechanisms. Mine is the last version with a semi-automatic aperture with 10 aperture blades. When I received it, the focus was rather stiff and it had oil on the aperture blades. It turned out that it is rather easy to service.

The whole optical system (with the aperture mechanism) can be separated by opening a single ring on the backside, using a lens spanner.

Now, set the focus to infinity and remove this screw (which is setting the focus limits).

Now, slowly(!) focus closer and closer, to the minimum (of 0.6m) and beyond, until the inner helicoid becomes able to rotate freely. For my lens this happened when the "m" was at the focus marker.

For the following, I keep the focus ring at the "m" mark. As seen from the front, I rotate the inner piece (slowly!) to see when it becomes loose and remember exactly where this happens. For this, I remember the position of the "upside-down" U-shaped piece (which is at the top in the picture below).

For my lens, this piece becomes loose when the"upside-down U-shape" is in the middle between the 2m and the 2.5m marks. This is exactly where it has to be inserted later!!

Now, I document the exact position of the focus ring. For this purpose, starting at the "m", I turn the focus ring clockwise, passing the "0.6m" up to the infinity mark. Then I continue to rotate the ring clockwise, and I check how far it goes before it comes to a stop. For my lens, this is exactly one more full turn.
Now I rotate it back by one turn (so it's again at the correct infinity position) - from there I keep turning, passing the 0.6m mark, until I reach the "m" mark (where the inner helicoid separated). From here, I continue to rotate it, until it comes out (for my lens after almost 7 full additional turns).

Now I got both helicoids separated - and, in the picture, already cleaned.

If you want to clean some of the glass, now is a good time to do that. You can access the rear element, by opening the ring on the back side.

To access the front glass and the aperture, you can remove the name ring with a rubber tool.

Open the outer ring (with a lens spanner) to extract the whole front glass.

Open the inner ring to access the front lens. 

At this point you can also access the aperture blades. I cleaned these in-place (without further disassembly).

When this is done, the lens can be reassembled. Since you remembered the exit points of the helicoids (you did! - didn't you?) you can put everything back together in the reverse order as described before. (Of course, with a touch of helicoid grease on the helicoids!)

And here it is:

Almost as good as new. Clean on the inside and outside and freshly lubed. Ready for taking great pictures. That's why we did this!

More of my lens repair tutorials can be found here.

Repairing a Canon FD 50mm f/1.4 S.S.C. Lens

The Canon FD 50mm f/1.4 S.S.C. lens is one of the sharpest 50mm lenses from its time. It has 7 elements in 6 groups and the aperture consists of 8 blades, resulting in a beautiful rendering of out-of-focus lights. This piece was made in March 1974. It is the older "S.S.C." version, made of metal (all-metal!). It feels so good - especially when compared to the later FD versions (with green distance scale), which are made of plastic.

Before I got this lens, I never liked the Canon FD lenses (based on the green plastic versions), but this is an entirely different thing. I did not plan to buy it - it came as part of a set with a Praktica camera and a few M42 lenses, and it was not clearly visible in the auction pictures. When it arrived, it was in horrible condition: The focus was completely stuck, the front lens was very dirty, and there was significant fungus on the rear elements.

But, it turned out to be rather easy to disassemble and clean this lens. The all-metal construction was a pure joy to work on, and I was so happy to be able to bring it back into almost mint condition (except for that scratch on the name-ring).

I documented to procedure in pictures. If you don't have experience with lens repair, please read tutorials about the methods for disassembling, cleaning and greasing helicoids, etc.
These pictures are supposed to speak for themselves - to help individuals who already have some experience in lens repair.

I'm starting from the front side.

This piece is adjusting the infinity focus. If you don't want to adjust it later, take a precise note and make a mark where exactly it was sitting!

And now, I continue from the back side.
This pin has to be pushed down, to rotate the breech-lock mount and access the screws.

All pieces - all cleaned - group photo:

Mount the lens on a camera, and use this piece to adjust the infinity focus.

Done! The lens is back to its former beauty - with a snappy aperture and nice, smooth focus. I added a nice retro-hood (55mm - to stop stray light, and for mechanical protection of the front element) and not it's ready to be used in the field!

More of my lens repair tutorials can be found here.