Filmwasters
Which Board? => Articles => Topic started by: cs1 on May 22, 2017, 10:00:57 PM
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I recently bought a nice Zeiss Ikon Nettar (01.jpg). It's the model 515/2 and it has the 10.5cm f/4.5 Novar-Anastigmat lens and Pronto shutter. After closer inspection I found that there was some dirt on the inner lens elements which I wanted to clean. This is how I disassembled the front lenses. Disclaimer: If you try to do this, do it at your own risk. I'm by no means an expert and I just wanted to share with you what I did with my own camera because there's very little information about this process when I searched for it on the net. If you have any advice what to do better, please let me know. :)
Here's the material that I used:
- The obligatory cotton gloves,
- a small flathead screwdriver,
- a small plastic spatula.
These are the steps that I took to disassemble the front lens:
- I turned the focus to the closest distance. The little pin on the focus ring touches the pin which prevents it from turning further.
- I used the small flathead screwdriver to unscrew the pin. (02.jpg)
- With the pin removed I could turn the focus ring (which also holds the front lens element) further. I turned it until the front lens came off. If you try this, a word of warning: make sure that you remember the exact position of the focus ring when it came off! If you don't you'll regret it when reassembling the lens.
- With the front lens element removed one can see the inner lens element. It's held in place by some sort of "tension ring". This ring has a small opening. With the plastic spatula (so that I wouldn't scratch the lens element) I pried the metal ring out of the socket that it sits in. This was quite a dangerous procedure because it's easy to scratch the glass of the inner lens element. Unfortunately my mobile didn't take the photo of this particular step due to the cotton gloves. Sorry. :( The ring and the lens element are still very obvious and it shouldn't be a problem to identify both.
- With the tension ring removed I turned the front of the lens downwards (I covered the front beforehand with one hand to catch the glass element) and the inner lens element came out. It's very important to remember the orientation of the inner lens element (which side faces to the front and which side faces to the back of the camera) because it's not symmetrical and it needs to be put back in the correct orientation during reassembly. Now the shutter leaves are directly accessible. (03.jpg)
- I cleaned the front and the inner lens elements.
- It's possible to access the inner sider of the back lens element by completely opening the aperture, setting the shutter to bulb (B), cocking the shutter, and holding the shutter release. It's not the most ideal way to do it but if one just wants to blow away some dust particles, this will do. (04.jpg)
- To reassemble the lens, I simply reversed steps 5 to 1.
The reason for the warning in step 3 is that, despite the fact that I thought I paid attention, I didn't pay enough attention to the position of the front lens when it came off. When I screwed the lens element back on, I couldn't turn it all the way to infinity because it was already screwed tight. When this happened, I unscrewed it again, lifted the lens element off the lens body at the exact position when it came off, turned it slightly clockwise "in the air", put it back on the lens body and screwed it back on. I had to repeat the process until I could easily focus to infinity and to the closest distance. Never use force here. If you can't turn the focus ring to infinity, something's wrong and you probably screwed the lens on at the wrong position of the thread. I had a photo of the correct position when the lens was set to infinity and there's only a really small gap between the focus ring and the lens body. It's really small but it's still there. So it's much better to pay close attention in the first place to avoid this fiddling. :) After the reassembly I used a ground glass to check the focus while holding the shutter open in bulb (B) mode. Now everything's nice and clean.
Lessons learned by me during this procedure: paying attention to when exactly the front lens comes off and taking as many photos as possible of the different states of disassembly because this can help immensely during the reassembly process.