// 2025-11-23 // by chrissy
Recently I got a wonderful old Contax FB camera. It is an old SLR camera produced by VEB Zeiss Ikon Dresden, the later VEB Pentacon Dresden. Mine is labeled with the name “Pentacon FB” so one can assume, that this camera was intended to be sold in Western Germany, where the trademark “Contax” was reserved for the cameras produced by Carl Zeiss and others equipped with Zeiss-optics.
The Contax FB has an included exposure meter working with a selenium cell (some sort of an early solar cell) and some other pleasing features like a mirror lock up and a automatic trigger of the iris aperture in the objective. So it was certainly one of the first modern SLR cameras.
Shooting a first Film for a test showed under- or overexposed parts especially in the right part of the picture.
A more detailed look to the shutter mechanism revealed that the first shutter curtain did not always open to its end stop. So it was necessary to have a closer look on the shutter mechanics.
Briefly, a two-curtain shutter constists of two pieces of black tissue, impregnated with some kind of rubber which makes it fully opaque. If the shutter is released, both of the shutter curtains are rolled up on their associated spring loaded spindle, with a defined time between the release of the first curtain and the second. If one is winding up the shutter mechanism, both are evenly pulled from their spindles and move to the right part of the err… I assume it’s likely called image-window. As this is done, the springs in die spindles get tensioned. Once the shutter gets released, the first curtain gets pulled immeaditly to its end stop while the timing mechanism (the small clockwork-shaped thingy) controls the timespan after which the second curtain is released. This controls the exposure time of an image. In my case, the oil, which was intended to lubricate the bearings of the spindles, has gotten quite sticky over time and maybe the springs had lost a little bit of their initial tension. Especially, when it was cold outside, the images I took showed this black section at their right side. So it seemed I should clean and lubricate this mechanism. Luckily there is a handwritten manual from Rick Oleson avialable at archive.org. [1]
To obtain access to the desired parts of the camera mechanism, one has to remove the front cover, the top cover of the camera as well as the film gate top cover. Starting with the top cover, remove the two knobs for winding up the shutter and the other one rewinding the film. Each has a single screw in it, which attaches it to its mount. Be sure to remove also the washers and springs located in the knobs. Clean these parts and store them, well sorted, in a safe place. After doing this, there come four screws to light. Remove them carefully.
Following up this, one has to remove the support foot under the lens mount.
After this, carefully lift the leather cover under the exposure sensor to get access to two small screws. After removing these, the top cover can be lifted from the camera body.
Be sure not do loose the small switch which selects between short and long time exposure and take care of the wire for the flash socket.
One might get the idea to desolder this wire. But in reality, this is not necessary. The flash-contact is simply mounted with a single, tiny screw. With removing this screw, the top cover might be placed at a safe place as we dedicate ourselfes to move further in our work.
Now we just need to remove the film gate cover. Nothing could be easier. It is attached by four screws, placed where the film cardige sits on the one side and where the exposured film gets rolled up at the other side. Remove these screws carefully, as there are four tiny washers under the film gate cover. You might find yourself trying to lift the cupver up, but it refuses to do so. Don’t apply force, there is a trick to remove it: Wind the shutter mechanism until the shutter cloths have moved approximately to the middle of the film gate. Then, and just then the clutch driving the film transport gear has the correct angle that the film gate cover can be lift up easily. If one now has a closer look to the mechanics, one may notice why we have to do so. If the driver has a rather vertical align, the film drive gear can easily slide out.
Now that we have achieved access to all of the parts, we need or want to service, we can move on.
I did not want to renew the shutter curtains. Despite all avilable information, telling the reader that the shutter curtains need to be replaced in any case, mine were in a quite good condition. So I decided just to clean and lubricate the mechanics that winds the shutter curtains.
The screws holding the spindle bearings in place, are safed with blue threadlocker paint. We loose them one after the other and take out the bearing. These bearings are loaded with a small spring inside, so when one looses the screws the bearings will rotate some rounds counter clockwise. I recommend you to count the number of turns, als this will help you later for the final adjustment.
Under the bearing there is also a really small washer. Take care of it, clean it and store it at a safe place until you mount it again. I washed the bearing in white spirit and cleaned the spindle shaft with a white spirit soaked Q-Tip. After the cleaning I applied a tiny drip of precision mechanics oil inside the bearing.
The other shaft on the lower side of the shutter curtain spindle cannot be accessed without removing the shutter curtains. In my case it was sufficient to trickle a little bit of white spirit in the gap between the bearing and the shaft, cleaning it with a dry Q-Tip and apply as a last step a tiny drip of precision mechanics oil with the help of a toothpick. Do not apply too much oil to precision mechanics, as it will attract dirt and eventually will result sluggish movement of these components.
After one has finished cleaning the desired components, it comes to the reassembly of the shutter mechanism. Carefully mount the bearings and don’t forget the tiny washers under them. Take care, that the tiny end of the spring fits into the slot in the shaft.
Now the springs need to be tensioned. You can do this using a small screwdriver in one of the slots. The springs are tensioned, if you turn the whole bearing clockwise.
First, we start adjusting the first shutter curtain. This is the upper one showed on the image. Rick Olesonrecommends, to tension it until the first curtain moves in a uniform motion to its fully open position. Then add one full turn where you might find yourself at likely 7 full turns. Cock the shutter and release it to check, if you are already at a sufficient spring tension. Do not overdrive it.
To adjust the second curtain, tension the spring until the curtain closes fully with a uniform movement and then add one full turn as well.
If you have done good in it, the shutter curtains sould move fast and without getting stuck on their way until their endstop. If you have some device to check the real exposure time you can now verify if the selected exposure times match the real ones. An oscilloscope with a small sensor consisting of a photodiode and a resistor would be sufficient for this.
At last I would recommend you, to safe the two screws holding the bearings with their springs in position, to apply a tiny drip of nail polish or dedicated threadlocker liquid. Be sure not to use high strength threadlocker, you might want to readjust the spring tension after a certain time!
To put the camera back together just do the steps from above in reverse and make sure to mount every of the small components at their intended destination. Take care of all the small washers and springs and do not tighten the small screws too much as it would damage the thread. I recommend you first to insert all screws on a part and screw them just for a few turns to make sure, everything fits in place before you finally tighten them.
And as a final hint, I highly recommend you to take your time, do not apply force anywhere. Every part should fit lightly in its place. These cameras are now roughly 65 to 70 years old and they deserve gentle handling.
Serviced like this, the shutter mechanism will fulfill its task for a really long time and you will have a camera for life.