carl zeiss jena tessar 70mm 3.5 - should i convert it?

Layer-cake · Joined: 18 Mar 2013 Posts: 560 Location: Cape Town

I got a Kodak duo six 20 in a camera set I bought. the camera itself isn't in great condition...the leatherette is coming off, there's quite a bit of corrosion on the body and the bellows look like they would need replacing to get it working again, but the lens itself is in good condition.

there's not a lot of info online about the lenses performance but I've been thinking about converting it to an M42 mount, it seems like it would be quite straight forward as the lens has its own helicoid already.

its not really a focal length I use as its a 140mm on MFT but I'll be able to use it on different camera in the future!! it doesn't seem to be a common lens, just saw a thread Attila did using a projector lens version for the tessar 70mm and the results where very nice but I don't known if these are the same.

any opinions would be appreciated:)

philslizzy · Joined: 07 Aug 2012 Posts: 4748 Location: Cheshire, England

With these old folders it is sometimes possible to unscrew the lens and shutter assembly and take it all off without damaging the camera. I'm not familiar with this model, but if you open the back of the camera while it is folded you ought to be able to see a retaining ring. This can be removed and the entire lens assembly taken off. Without damaging the camera at all.

A plastic plate with the appropriate size hole in it can mount the lens/shutter assembly and an adapter of some sort glued to it. I'd attach it to a t-mount of my choice and fit it to a bellows. Use the bellows for focusing. Unless you want to make a rigid tube and focus using the front element.

Set the shutter to T and it will remain open until pressed again. Alternatively if the shutter only has B then use a locking cable release to keep it open.

Good luck

Alternatively this idea may work...

https://www.flickr.com/groups/89209252@N00/discuss/72157600032755971

Layer-cake · Joined: 18 Mar 2013 Posts: 560 Location: Cape Town

HA:) thats kinda epic with the whole camera stuck on the end! I see what you mean, the lens does indeed come off with a retainer ring, getting the section with the helicoid off would be a bit more work.

I have a couple of options available to me for the conversion, what I'm really wondering is more about the lens itself, its kinda slow but it does have a nice 10 blade aperture system. I have a 75mm c mount lens that I have in this focal range and it barely sees any use as it is.

philslizzy · Joined: 07 Aug 2012 Posts: 4748 Location: Cheshire, England

Does the whole shutter assembly come out?

Leave the lens in the shutter - thats where the aperture is. Taking it out of the shutter will cause major problems as the spacing between the elements has been calculated carefully.

Ian should know more about this and may reply if he sees this thread.

Your problem using the whole camera approach is that the lens is fixed into position when the camera is opened, allowing only macro as the sensor will be a few centimetres from the camera film plane.

The camera shown in the link can be used because the bellows can be adjusted for length.

The Tessar, in my opinion, is likely to give sharper results than the c mount lens as the image circle is much bigger than the c-mount, leaving the blurred edges far away on your MFT sensor (I assume it is). Both lenses will have different characteristics making each better than the other in its own way. The Tessar is likely to be very low contrast.

Layer-cake · Joined: 18 Mar 2013 Posts: 560 Location: Cape Town

Sorry Ian, I didnt actually realize you had replied, well the whole lens bit did come out but I wanted to retain the focusing mechanism of the lens itself and adapt that.

Managed to do a not so bad job of this using a T2 adapter and attaching the lens to that

Managed to get the lens to focus a mm past infinity, which is the way I like them and it tuned out quite small, not the fastest lens but pretty cool looking and it's an M42 mount now;)

philslizzy · Joined: 07 Aug 2012 Posts: 4748 Location: Cheshire, England

Nice job! and reversible?

Layer-cake · Joined: 18 Mar 2013 Posts: 560 Location: Cape Town

yeah I could reverse it but the body is old and would need an overhaul, bellows worn, some rust and other oxidation on the body. got it from a guy near Durban here and that place destroys cameras with the heat and humidity unfortunately!!