Repairing a Carl Zeiss Jena Pancolar 50mm f/2.0 lens

 

The Carl Zeiss Jena Pancolar 50mm f/1.8 is a legendary lens, famous for its color rendering and for its sharpness, wide open. It features a double Gauss design with 6 elements in 5 groups. But this article is about the earlier version with f/2. It was announced in 1960 as an improvement of the equally legendary Carl Zeiss Jena Biotar 58mm f/2 (the one that was cloned in Russia as the "Helios 58mm f/2) which increases the diagonal angle of view from 40 to 46 degrees. It featured 6 elements in 4 groups and uses lanthanum flint glass. There exist different versions of this lens, the earlier ones had a focus ring with rubber, while the later ones were in the "Zebra" style. A very detailed description of the development of this lens can be found on this incredible web page (in German, but Google will translate it).

My piece was made between 1967-70, it is the "Zebra" version with Exakta mount. It came with super stiff focus and aperture, but I knew that those would be very easy to fix - and it turned out that it was even easier than I expected.

General Recommendations

First, you need tools like a lens spanner and (good!) screw drivers. For cleaning the metal surfaces, I am using cotton swabs and high percentage Isopropyl Alcohol (I got 91%) for all metal surfaces and the glass - and lighter fluid (Zippo) for cleaning the old grease in the helicoids). You also need helicoid grease.

I strongly recommend to take photos of every single step along the way. Whenever I take off a piece, I first try to understand how it was connected and what it did, and then I clean immediately all of its accessible surfaces with alcohol-soaked cotton swabs. 

Disassembly

I tried to document the whole process in great detail through the pictures below.

Starting from the front side.

At this point, you already have access to the aperture blades.

At this stage I had some trouble since two of the four screws didn't want to come out. But I soaked them in alcohol and lighter fluid and waited a few days. Suddenly the third screw came out... and two days later the last one too. (Sometimes it pays off to be patient!)

My lens spanner had the wrong angle to get into this slot. But I was able to get the ring out using two screwdrivers.

With the ring removed, you can extract the rear glass piece - and with a lens spanner you can take out the last element.

When the aperture ring is removed you can see the little gear that moves the ring with the depth-of-field pointer.

This ring is rather thin. Be careful not to bend it when removing it.

Before removing the gear: remember exactly in which orientation it was sitting there - take a photo (and/or look closely on my photo above).

Back to the front side. First take out the piece with the aperture - and then the focusing helicoids.

Now is a good time to clean the aperture blades. I was able to do so, without further disassembly of the aperture.

Take out the helicoid key (and, before you do so, make sure to set the focus to a defined value - e.g. to the minimum focus distance).

While holding the focus ring fixed extract the inner helicoid (slowly!) and make sure you note where exactly it exits. Mine did so when the slot for the helicoid key was exactly at the red 2.2ft mark (see picture).

At this point, I rotate the focus ring to infinity - then I remove the screw (at the top in the picture) that sets the limits for the focus. Now, I first check how much further the focus ring can be inserted before it comes to a stop: In my case I can rotate it beyond infinity by  1 1/4 turns. Then I bring it back to the original infinity setting. From there, it takes 6 1/4 turns before it comes out. For your lens, this may be different - so, make sure to take pictures, sketches, and notes!

Everything is disassembled and cleaned!

Just three little 'drops' (much less than a water droplet!) for the outer helicoid (= the focus ring). Of course, the exact amount depends on the type of grease.

When the focus ring is in the correct position, put back the limit-screw. Then the inner helicoid can be greased and inserted.

Putting back the helicoid key,

the aperture piece,

the gear and the ring with the d.o.f. pointer,

and the aperture ring.

All glass surfaces are cleaned.

Suddenly, these two pieces cam out. It turns out that (unlike almost any other lens that I ever encountered) the clicked aperture ring is not using a ball, but this pin and the metal piece as a spring. The latter has to be inserted into the grove of the aperture ring.

And that's it! A wonderful lens is back in great shape! 

Images

Here are a few impressions of my first shots that I took with this lens on a Sony A7Rii. Some are wide  open, some at f/5.6. 

I really like the rendering of the out-of-focus regions.

More of my lens repair tutorials can be found here. 

Repairing a Meyer-Optik Görlitz Oreston 50mm f/1.8 Lens (2nd Zebra Version)

The Meyer-Optik Görlitz Oreston 50mm f/1.8 lens is a legendary lens. It is famous for its painterly bokeh wide open, and for it sharpness when stopped down. The early versions of this lens have both the aperture and the focus rings in "Zebra" style - this later version has only the aperture ring in (a different) "Zebra" style. This piece was made around 1969.
Usually, for these old lenses the old grease became stiff, making the focusing hard - plus: oil on the aperture blades causes the aperture to get sticky and close either slowly or not at all.

General Recommendations

First, you need tools like a lens spanner and (good!) screw drivers. For cleaning the metal surfaces, I am using cotton swabs and high percentage Isopropyl Alcohol (I got 91%) for all metal surfaces and the glass - and lighter fluid (Zippo) for cleaning the old grease in the helicoids). You also need helicoid grease.

I strongly recommend to take photos of every single step along the way. Whenever I take off a piece, I first try to understand how it was connected and what it did, and then I clean immediately all of its accessible surfaces with alcohol-soaked cotton swabs. 

Disassembly

Here, I show the pictures of the disassembly and cleaning of my Oreston.

It starts with loosening the little screw (below the "O" of "Oreston") - just loosen it, don't take it out. Then you can unscrew the front piece by hand and, with a lens spanner also the front glass piece.

On the back side, removing the three screws lets you take off the back piece and then, the aperture ring (don't loose the little metal ball that comes out - it's for the aperture ring's clicks).

Warning! There are three small grub screws holding the rear glass piece on the left. And it seems like you could take these out to separate the rear glass and to get access to the rear side of the aperture. But don't do it! Don't open these! In fact, these grub screws are used to align the rear optics - and once removed, you will never be able to align the optics again, as this requires special tools.

I set the focus ring to a defined value (I pick infinity) - then I remove the helicoid key.

Careful: Now the helicoid can rotate freely - don't "play" with it, but keep it in its current position.

Before taking out the coarse helicoid, remember where it was (take notes & pictures). Then slowly rotate it out and remember exactly where it became free (this one was cleaned already before I took the picture - yours will likely have old dark, sticky grease on it). 
The helicoid piece also holds the aperture mechanism. If you wanted, you could take out the aperture blades (from the front), clean them (carefully!), and reassemble them. The last step can be difficult and time consuming - that's why I always try to clean the aperture blades in-place. I put lighter fluid on a cotton swab and rotate it around the closed aperture - open and close the aperture - and repeat this 20-40 times (always using new cotton swabs) until it looks clean and moves without resistance. This ususally works very well, and a full disassembly is not needed.

These two screws are setting the limits for the focus ring. Before removing those, I make sure that the focus is still set to infinity. Before unscrewing the fine helicoid, I always test (and take a note) how many turns it could be inserted (i.e. rotated clockwise) until it comes to stop, starting from infinity - and then, how many turns it takes to come out, and at what position it exactly comes out.

Cleaning both helicoids with 91% IPA and/or lighter fluid.

Using small amounts of lube, first insert the fine helicoid (the focus ring) and make sure it sits exactly at the infinity position before you removed it.

And the coarse helicoid too. 

Put back the helicoid key, ...

... the aperture ring (with the ball!), ...

... and the rear piece.

Before assembling the front, you may want to extract the front lens and clean it, if needed.

This lens is finished! While it can't hide its age, it will function for many years with clean glass, a snappy aperture, and smooth focus - and inspire someone to take great pictures! 

More of my lens repair tutorials can be found here.