The Zeiss Ikon Universal Juwel is a folding view camera from the 1930s. I have the 275/5 model, designed for European continental 9×12 format film sheets or glass plates. It has an uncoated Zeiss Tessar 4.5/150 lens in a Compur shutter.
While 9×12 cm format film is still available, it is not nearly as common or versatile as the slightly larger US standard 4×5 inch format sheet film. I would like a (reversible!) way to convert this lovely old camera to use 4×5. The Tessar certainly projects an image circle large enough to make it possible.
Sourcing the 4×5 back
Now, one of the most important features of the Juwel is the rotating back. Almost all other contemporary Zeiss camera were in portrait (or, rarely in landscape) orientation, ie. they were rectangular cameras. The Juwel is quadrilateral to allow the back to rotate between portrait and landscape orientations.
So, off to the internet to find a rotating back in 4×5 format that’s a similar size to the rear of the Juwel. A bit of research led me to the Toyo rotating back.
The Toyo 45 Graflok 360° rotating spring back is from a Toyo Field 45A camera, and they are fairly common on eBay as parts. I managed to pick a decent one up for around US$120. It includes a ground glass and hood, and can be used with all standard 4×5 Graflok film holders.
Swapping the backs
After removing the existing back from the Juwel and checking physically what I had surmised from my research, I was relieved to find that it was indeed going to be possible to fit the Toyo to the Zeiss. They have almost identical corner to corner dimensions. The only ramification seemed to be that the film plane would be moved back about 14mm.
The existing rotating back is attached by four screws, one in each corner. The Toyo back does not have holes as it’s designed to attach to the 45A by clips. The next step is to add some screw holes to the Toyo in the matching spots. These are then countersunk to allow flush mounting.
I removed the original back screws from the Juwel and took them to my local Bolt Barn to see if they could match them in the length I required. They scratched their heads and sent me to the hobby shop. I had hit my first hurdle: these screws turn out to be tapped with an utterly obscure pre-war german opticians’ thread and are simply impossible to source.
My next option would be to modify the threads on the body to be something that would be compatible with a metric screw. The downside of this plan is that the body would no longer be completely original. (Some may even consider it vandalism.) Balanced against this is the fact that the body is already modified by the retro-fitted rangefinder. Additionally, I am much more likely to use this camera if I can put, say, Portra 400 4×5 film in it, rather than the few B&W ISO 100 stocks available in 9×12 format.
After careful consideration I decided to go ahead with this plan, and retapped the holes in the body with M3 threads. I then sourced screws that can be used attach either the original 9×12 back, or the Toyo. As modifications go, it’s pretty invisible once the back is attached.
There is a slight gap between the backs, as you might expect, but surprisingly it is less than a millimetre. I used some light seal neoprene material to make sure no light leaks remain. Unfortunately my material run was a little short but I was able to overlap it slightly. It now seems light tight in my tests.
Attaching the back was straightforward at this point.
So here we have a working 1930s German camera with a 1950s American rangefinder and a 1970s Japanese international standard 4×5 back, still good to make images with in Australia in 2019. This is why I love large format photography.
I mentioned earlier that the only complication seemed to be that the film plane is shifted backwards by ~14 mm. Given that this is a view camera, and if we are focussing on the ground glass, there is no further issue.
However, there are two other built-in methods of focussing on this particular camera.
We can recalibrate the rangefinder to meet the new film plane quite straightforwardly, and I will cover this in a later post.
The bed of the camera has an ingenious hinged focus scale mechanism, which locks the lens standard to infinity when it is extended to exactly the correct length. It then gracefully moves aside when you rack the focus knob.
Of course, now that my film plane is ~14 mm further back, so is the lens standard, and therefore this little beastie is in the wrong spot!
My solution for now is to simply remove this part of the camera and focus via rangefinder and ground glass alone. Eventually, I want to mill a new piece of 1.5 mm brass strip to replace the one in the picture, and then tap it appropriately so I can reattach this focus scale in the new position.