History

First of all this is a completely different lens from the more well known, mass produced East-German post war CZJ Biotar 50mm f/1.4 which was made for the Pentaflex AK16 film camera. That 1950s lens was made for 16mm film, which makes the image circle smaller than the pre-war cine lens made for 35mm film. At first glance it can be easy to mix these two lenses up, the easiest way of telling them apart is that the post war lenses focal length is written as millimeters and the pre-war is written in centimeters.

Finding information about this lens was surprisingly hard for being such a well known name, but maybe that’s what made it hard. Hard to filter out all the information on the more famous Biotar lenses. But from a lot of digging I found some very interesting and for me at least new information.

The seller who sold this camera and lens to me said it was a World War 2 Luftwaffe camera, but those usually were fitted with the mass produced CZJ Biotar 4cm f/2. So I kind of knew from the start that this was something way different. The camera didn’t even have a viewfinder of any kind and things like the shutter button were just gone. The serial number of the camera didn’t match up to the Luftwaffe serial numbers either. When I got the camera I found out the camera didn’t even have a shutter mechanism. All the shutter button did was to push the film roll forward. I had suspected it was an X-ray camera before I received it, but this was definitely a very strong proof.

The camera is a Berling Robot II camera from 1943 and the lens is from 1939. After some research I found out the camera is an X-ray camera used in tuberculosis screening equipment at the companies Sanitas, Berlin and C.H.F.Müller, Hamburg. The frames it took were a so-called half-frame format, being 24x24mm. The camera uses normal 135 film, but because it’s a square format you get way more images per roll. Which would be preferable for such a system I guess. Some sources said this camera came either with this CZJ Biotar 50mm f/1.4 lens or a Leitz Xenon 50mm f/1.5.

At the same time as this lens was made and used, doctors and scientists also used the other X-ray lens Carl Zeiss made in the 1930s. The CZJ R-Biotar 55mm f/0.85. But from one source it’s stated that many preferred the more sharp, easier to use Biotar 5cm f/1.4 in their work.

How this little obscure camera came to my little country of Norway, we might never know. But I can assume it might have gotten over the borders during the German occupation of Norway in 1940-1945. I can assume these smaller X-ray systems would have been easier to take with you to less developed countries.

The lens is said to be optically identical to the original film lens Biotar 5cm f/1.4 which was first used on the Carl Zeiss/ICA Kinamo 35mm film camera. The difference is that the X-ray version is stripped down, taking away things that might have made the original cine lens more expensive, leaving just the lens block. In one source from Thiele it’s stated that there were only ever made around 200 of this stripped down X-ray version of the original Biotar 5cm f/1.4. There exists also a stripped down X-ray version of the Biotar 7.5cm f/1.5 lens which was made in the same period. Of these 200 units that were made, the later ones were marked with the then new red T markings.

Adaptation

To use this lens on a modern camera I had to figure out a way to remove the lens from the camera body. It was basically a fixed focus system, but you could do small focus adjustments by adjusting the threads, either unscrewing a bit or tightening it. Originally I wanted to use as many of the parts as possible, but it was too awkward to adapt this focus part directly to the camera as it would have taken ages to go from 1 meter to infinity, if that even would be possible with this. So I unscrewed this focus part and was left with the bare cine block. Mind you this lens has no aperture, as this version of the lens was specifically designed for X-ray and other scientific/industrial use.

Originally there was a nice solid heavy brass part with threads in the front of the lens that I assume was to mount the camera to the X-ray machine. The threads on this part were smaller than the threads of the filter threads of the lens, so it actually made the image circle a lot smaller. So I ended up removing this piece too, there was no glue, no screws or anything holding this piece together, it was simply pressed onto it, keeping it safe only with friction. This was the hardest part to remove because it was very well fitted, but with patience I managed to remove it from the lens block.

Adapting this lens to my Sony A7RII was pretty straightforward because of the threads at the middle of the lens. Unfortunately these threads are non-standard, fortunately for some reason one of my old M42 extension rings managed to secure the lens, even with wrong diameter and thread pitch. It didn’t damage the original threads either, so I was happy with this solution. In the future I will get it machined professionally to get a nice adapter to M42 or something else.

With a stable M42 mount I could choose whatever focus helicoid I wanted, I found that the old original M42 Pentax helicoid extension tube felt the best. Then I used one of those cheap slim M42 to E-mount adapters. I generally don’t like to add aperture blades, just because you more often than not have to modify and cut the original lens which would damage it. I prefer to always work non-destructively and preserve the historical value of it. Another argument for not damaging or modifying old lenses is that in the future new systems will come and future photographers will be very mad about many of us for damaging lenses like that. I’ve experienced that from time to time, where adaptions done in for example the 1970s, where they’ve damaged their original lenses to make them fit some extinct camera system.

Image Characteristics

First off the lens is sharp, as sharp as you would expect a classic double gauss to be. The corners are as expected to be less sharp. Chromatic aberration is at a normal level for lenses from the 1930s. Contrast is pretty good if you use a lens hood, the lens is uncoated so it can be challenging shooting if the sun hits the get to bounce around inside the lens.

It covers a full frame sensor quite nicely, but it will vignette a bit, but has no black corners. This vignetting you can easily reduce or remove in programs like Adobe Lightroom when shooting in RAW format. Even though the illumination circle cover full frame, it’s clear that the image circle is smaller. Which makes sense as the lens was designed for 35mm cine use, meaning S35 or APS-C format. I later adapted the lens to my GFX 50S to test how the coverage was on this bigger sensor. It wasn’t the best as expected, but it can actually be used if you crop your image 1:1. With this the lens acts more like a 46mm f/1.3 lens, so not much different.

The lens is small and lightweight, which makes it very pleasant to operate. It has a pleasant bokeh like most double gauss lenses with a slight swirly bokeh. Nothing crazy swirl like the newer post war Biotar and Biotar copies are famous for today. I do feel the lens performs best in black and white, probably because it was never meant to be used with color film.

I used this lens on a small film project and it turned out to be a great lens to film with too, as expected. I used variable ND filters to compensate for the lack of aperture control. The lens flares are really beautiful on video where there is more motion.