Repairing a Carl Zeiss Jena Triotar 135mm f/4 lens

In this post, I give detailed instructions how to disassemble, clean, and re-lube the early, slim version of the Carl Zeiss Jena Triotar 135mm f/4 lens.

The Carl Zeiss Jena Triotar 135mm f/4 lens was created in 1938 for 35mm SLR cameras. Production was stopped in 1958 after Zeiss rediscovered the Sonnar in 1957. It is a triplet (3 elements in 3 groups) and it was made with Exakta and M42 mounts. The earlier version (top) is slimmer while the later more common version (bottom) with preset aperture is much wider. Both have 15 aperture blades.

Most pieces that you can find these days have in common that their focus and aperture rings are very stiff. In the piece that I got, the focus was completely stuck, and when trying to turn the focus ring, you could hear the grub screws scratch over the metal (ouch!).

Please read all of the following before you start, to get an overview of what tools are needed during the procedure. Also, you may find that you could do things in a different order. I have the habit of cleaning every single piece of a lens - every screw and every surface. I'm using paper towels, cotton swabs and 90% isopropyl alcohol and/or Zippo lighter fluid.

I start with loosening the three grub screws on the focus ring (1.), which then slides to the front. Be very careful that these don't come out! They can easily get lost (that's why I worked on rubber mat) and it's a pain to insert them again (believe me, it happened twice to me). This gives access to the two "guide screws" (2.) which "guide" the focusing helicoid. If you unscrew those, you can remove the helicoid. Be very careful to check and note where it exits, since there are 12 entry points and only one will give you the correct focus range (and reach to infinity).

Now you can also remove the focus ring. In the back piece, you can see a black ring which is screwed to the focus ring. This defines the limits within which the focus ring can be rotated.

By removing this screw, that ring becomes loose ...

... and one can unscrew the focusing helicoid (remember the positions of the rings before unscrewing the black ring, and to count the number of turns before the fine helicoid exists - make sketches and take photos!). Now the fine helicoid can be cleaned.

I continue with the front piece.

The front element can be easily unscrewed - then the aperture ring can be removed after loosening (not removing!) the three grub screws (as you can see in the picture, mine is missing one, but that's good enough to hold it).

With the aperture ring removed, you have access to this screw (3.).

When this is removed, the black ring (which controls the aperture) can be unscrewed.

Here you can clearly see that it was the old sticky grease which caused the aperture ring to move so poorly. 

I made a very thin scratch on the black metal, to note the position where the red arrow was pointing at. After removing the grub screws (4.) the silver ring can be removed and you get full access to the helicoid.

From the front you also get access to the aperture blades. Surprisingly, mine had no traces of oil (yes, they look dirty in this picture, but there is nothing that comes off with lighter fluid on a cotton swab).

Now the lens is fully disassembled (... at least as far as I plan to disassemble it...).

Now, I make sure to clean everything as good as possible, especially the helicoids. And then, I do all steps in reverse order.

I place the wide silver ring over the front piece, align with the scratch that I made, and tighten the grub screws (one can later still re-align this, if needed).

I put a really tiny amount of helicoid grease on the (cleaned!!) threads - only three small drops at three different places, separated by 120 degrees. I use as little as possible - any excess makes it harder and harder to turn. At the end, the screw is inserted again...

... and the aperture ring is fixed with its grub screws.

And I check that the full open aperture corresponds to the "4" setting. 

Now, I work on the focusing helicoids.

Again: I use only tiny amounts of grease. First, on the fine helicoid, which gets inserted (with the black ring in-between).

In the right position, I fix the screw that holds the black limit-setting ring.

I put a (small!) amount of grease into the coarse helicoid, place the focus ring in between...

... and insert the helicoid exactly where I noted where it came out. In the final position, the slits have to align with the holes for the guiding screws.

When this is achieved, I insert the guiding screws....

... slide the focus ring back, and fix it with the three grub screws.

Now, the lens is ready!

I still have to clean the front element - but that's another story.

Complication

The above description should usually work. In my case, however, there was a really unexpected problem in the very last steps: I was not able to insert the "guide screws". 

So, I took the focusing helicoid apart, and I noticed that their flat (unthreaded) end, which is supposed to fit into the helicoids slits was too wide - and didn't fit.

It's also suspicious that both screws look slightly different...

First, I was a little hesitant, but then I filed the ends of the screws down until they matched the slits.

Of course, I had to be careful not to harm the threads! But it worked!

Washington, DC

Spending a few days in the area, I had the chance to visit Washington DC for one afternoon. Initially, the rain was annoying - but afterwards my photos benefited from the clouds and puddles.

Road Work Ahead

This "Road Work Ahead" sign and its shadow has fascinated me over a few years.

I have used the top picture for the title page of my book "Construction, Building, Work in Progress"

In a Thrift Store

When spending time in a thrift store, why not take some photos?
Pergear 25mm f/1.8 and Zeiss Flektagon 35mm f/2.4 lenses on a Sony NEX-6 body.

The (so-far unnamed) prop from "Asteroid City"

When watching the trailer for the new Wes Anderson movie "Asteroid City", a few things caught my eye: In the first place, of course, the beautiful colors, then the rangefinder camera (which also got the attention of others), and then ... that wonderful, minimal, mysterious prop (at 51 sec).

"What do those pulses indicate?"

"What? Oh, the beeps and the blips? We don't know."

If you ever visited my blog, you may have noticed that I love building movie props with light and sound effects. So, naturally, I started thinking about how to build this one. 

The first step is always about collecting all available information. So far these are the images from the movie trailer, plus one other image that I found on the web.

The eight digits are updated from the left to the right in 0.1 sec intervals, and then the display stands for half a second (I got that from counting frames in the trailer).

In another clip, one can see the following two patterns alternating - this looks like a warning/alarm signal.

 

The left one is blinking three times and then the right one is blinking once. (They are on for approx. 2/3sec and off for approx 1/3sec).

Getting the Dimensions

With these images, I think, I captured all the different light patterns that can be seen in the trailer. 

To estimate the size of the prop, the perspective in the lower images helps to use the chair as a reference. Comparing this to my office chair, it seems that the prop is about 2 feet wide.

With this in mind, I use one of the upper images to look at the details.

And it seems to make perfect sense that the spacing of the lights is one inch (which makes the spacing between the eight modules 2"). With this, the prop should have a width of 24 1/2" and a height of 7". The two feet have a distance of about 16" and a width slightly less than 1" (consistent with the thickness of 3/4" of typical pine boards). 

The Electronics

The whole unit will be operated by an Arduino Pro Mini microcontroller. The lights are operated by power shift registers TPIC6B595 which can sink up to 150mA for each channel. Based on the following image, I think that regular (5mm) LEDs are too small.

But 8mm straw hat LEDs look much better (and the "straw hat" type provides a wide viewing angle). With 1" spacing, the six LEDs of each of the eight digits fit one 5cm x 7cm PCB.

And they can be very bright (0.5W / 150mA). I will, however, not operate them at full brightness. With current-limiting resistors of 68 Ohms, each LED will draw about 30mA and still be bright enough to be visible in a bright environment. If (on average) 24 out of all 48 LEDs are on, the whole unit will draw 0.72A - this is what typical USB chargers can easily provide. 

By connecting the "enable" pin of the shift registers to one of the Arduino's PWM pins, one can later reduce the LED brightness as required. 

Building the Enclosure

The enclosure is built from 3/16" plywood using a laser cutter. It is designed such that the front plate, the top and the sides do not have any slots or tabs, to avoid having to spackle and sand those. Only the bottom and back piece feature slots and tabs. 

I start, mounting the enclosure base plate on a foot. If we assume that the unit in the movie is placed on ground level, that foot would be about 3 feet tall. However, since I would like to keep this not too large, I will make the foot 1 ft tall. This way, it can sit on a desk or a shelf. The foot is made of two pine wood 3/4" x 3/4" square dowels screwed and glued to a  1/2" plywood base. 

Fresh from the laser cutter: the other pieces for the enclosure.

The choice of the paint colors is not easy, as the images from the movie trailer are not taken in natural light. While the front plate is clearly black, the outer sides may have some color. But I assume that this comes from the light conditions, so I decide to paint the outside white. 
To avoid painting at the boundaries after the unit is assembled, I paint the front plate and the edges of the bottom/top/sides before gluing. Then, the back plate is glued to the three pieces that provide the internal structure. The whole thing is glued to the base, and the front plate is added.

Then, the sides and the top piece are added and everything is painted.

Little spacers are added behind the front plate for mounting the PCBs of the LED boards.

Assembling the Electronics

 The electronics is distributed over 9 PCBs: One that has the Arduino and eight for the LEDs for each digit. In the first step, the LEDs are soldered in place using the openings in the front plate as a guide.

Then I finished the PCB for the Arduino, and two of the LED boards.

I wrote some test code, and (surprisingly!) it worked.

Then the other six LED boards are finalized, ...

... and the whole unit is assembled.

Before watching the movie, I can only rely on light patterns that I saw in the clips on the web. So, I programmed the Arduino to display random light patterns, randomly between 12 and 30 times, and then once the "alarm/warning" pattern (as mentioned above).

The Final Unit

 I took the finished unit to several location in out town to take these photos.

And here is the "making of" video, which also shows the prop in operation.