Contax ii body and lens cleanup

[Crysist]

Fun update: I found a pre-war Carl Zeiss Jena 35mm f/2.8 Biogon. I got it at a good price but only because it was dirty and didn't work completely. Can't get it to mount all the way and the rings are all stuck. Also a tiny piece of the barrel right next to the locking button has a little crack in it.

Anyone here have experience getting a lens unstuck?

 

[1957ExaktaVarexIIa]

If you should have a postwar Contax: The prewar 35mm Biogon (and postwar Jena Biogon) does not fit on postwar cameras. Because their shutter material had been modified, their mirror box had got a bit smaller.

There was a new postwar 35mm Biogon created at Zeiss Oberkochen ("Zeiss-Opton" or "Carl Zeiss", instead of "Carl Zeiss Jena").

 

[Crysist]

If you should have a postwar Contax: The prewar 35mm Biogon (and postwar Jena Biogon) does not fit on postwar cameras. Because their shutter material had been modified, their mirror box had got a bit smaller.

There was a new postwar 35mm Biogon created at Zeiss Oberkochen ("Zeiss-Opton" or "Carl Zeiss", instead of "Carl Zeiss Jena").

Both the camera body and the 35mm Biogon are prewar. The barrel is out of place in some weird ways, the focus goes past infinity and stops before the minimum distance and the locking tab is out of place.

 

[Crysist]

So here's an update: after much searching, I found a video that shows how to disassemble the lenses of a pre-war biogon:



I got the special rubber lens wrenches that they worked quite well once I overcame how tight some parts were screwed together. The back section eventually came off and I cleaned it a bit, but not much needed so I focused on the front. It didn't seem to budge. I resigned to use one of those caliper using tools for retaining rings on the front when the rubber things weren't seeming to cut it. Well... that slipped and thankfully only scratched a tiny bit of paint, unfortunate though because it was all otherwise unmarred before. Still, the glass didn't get hit.

So now I've sworn off the evil torture device looking thing for removing retaining rings and am back to the good ol' Japanese rubber cone thingies. Uhm, would you be mad at me if I told you it loosened the next time I tried turning it?

I found it's mainly the front element that has some annoying haze. There was some fungus floating somewhere that I couldn't seem to reach with my cloth. The haze "felt" the same, even though it lit up on the front element really bright in the light. Couldn't feel a texture difference with my fingertips. A bunch of scrubbing (lens cleaner + microfiber cloth) didn't get it off.

Either way, I reassembled it and it did in fact look clearer. Besides maybe a tiny bit of fuzz that might have been left by me. I'll need to get better at this.

Also, this might be strange, but the issue with the lens barrel does NOT seem to be an issue for using the lens. Seemingly.

I don't know if I had done it wrong before but I was able to mount it halfway (the red dot is at 1 o'clock instead of 12). And I was worried about whether this issue with the barrel would screw things up with the focus. Then I realized: the focus helicoid is all that matters, not the distance scale. If it's pressing the coupling mechanism by something directly attached to the lens groups, it should still be "accurate", no?

First things first, the focus ring move the focus patch. So that's good.

Then, focusing on a bright light at infinity causes the lens to stop here:

Unmounted it turns a tiny bit more, so the infinity tick is over the 2.8 tick. There's still an issue with the aperture being stiff, which might be understandable because it's difficult to turn, but it's not as easy as all these other videos that I thought mine might be entire stuck.

So, despite all this strangeness, things seem like they can work. Of course I'd like to know how I can fix this issue but I'm gonna see how this fares!

 

[Donald Qualls]

To feel unevenness with your fingertips, it would need to be close to 100 times the height of what will show as haze in transmission or with a raking reflection.

 

[Crysist]

To feel unevenness with your fingertips, it would need to be close to 100 times the height of what will show as haze in transmission or with a raking reflection.

Our fingertips are extremely sensitive to textures, I figured I would have felt something. At the same time, glass needs so little to become completely diffuse by etching or sanding it...

I used this small bottle of kodak lens cleaner that's just water and ammonium carbonate. But maybe it's only enough for cleaning and not able to do any polishing.

If the haze is only visible with raking light at such an angle, might it be mostly invisible? I do have to put it up to a light or over something dark to see the haze now. Otherwise, is there anything else I could do to try to fix it?

And I still need to fix the barrel being wonky, the locking clip twisted off its little cutout, and whatever else is keeping it from mounting all the way to the 12 o'clock position.

 

[Donald Qualls]

A solution of ammonium carbonate will be alkaline, but have no abrasiveness -- the impurities are at molecular scale, several orders of magnitude smaller than the thickness of a lens coating.

Most likely all that you'll get imagewise from an etched surface is flare -- not those spectacular internal reflections Michael Bay likes in his CG shots, but just scattering light that will tend to reduce contrast and fill in shadows.

 

[Crysist]

A solution of ammonium carbonate will be alkaline, but have no abrasiveness -- the impurities are at molecular scale, several orders of magnitude smaller than the thickness of a lens coating.

Most likely all that you'll get imagewise from an etched surface is flare -- not those spectacular internal reflections Michael Bay likes in his CG shots, but just scattering light that will tend to reduce contrast and fill in shadows.

Ah, I thought a carbonate would be abrasive because I was thinking of calcium carbonate.

Is there anything I can/should do for this kind of haze if I do want to try to fix it?

 

[Don_ih]

Is there anything I can/should do for this kind of haze if I do want to try to fix it?

You would need to polish it using cerium oxide. Ideally, you would make a pitch lap and use that. The cerium oxide should be optical grade and made into a paste. I used some to remove the impenetrable haze from the inside of an Elmar 50 M lens. I made a pitch lap using a piece of violin rosin. It worked. Some people use the cerium oxide on a q-tip. As long as you polish the entire surface relatively easily and only enough to remove the haze, it'll be good. The lens will still flare - but not as badly - and you'll want a hood.

I'm not completely satisfied with how the Elmar turned out. But you could see nothing through it when I got it.Now, it's clear but there is no coating whatsoever on it. It certainly gives things a Leica "glow"...