Contax IIIa curtain tension

[Crazy Fedya]

Hello, everybody!
I was wondering if anyone knows how to reduce lower curtain spring tension in Contax IIIa without taking it apart or sending it away. There is a screw by take-up spool, but that only increases tension. I would like to reduce it, because it kind of jerks the camera, when shutter is being released.

[Vickko]

yeah, that is the issue. The screw tightens the tension. You gotta take it apart to get to the shutter module to release the tension.

[Crazy Fedya]

It kind of doesn't make sense. Like a car transmission without a reverse.

[sevo]

There is a small catch on a screw that prevents it from unwinding.

[Dez]

You can also reduce the tension by turning the screw in the opposite direction, but you need to push the little spring catch out of the way to do it. This is much easier if you first remove the shutter cover- easier than it looks. One frustrating thing about Contax shutters though is that there is not a separate tension control for the two curtains- that screw works on a common spring. Shutter speed is determined primarily by the slit width, which is a function of the two curtain releases under the top cover. Getting the high speeds right is difficult, made worse by the rather dubious design which has much of the film wind train also operate when the shutter fires. Any drag in this gear train will make the high speeds unusable. The gear train must be in perfect shape, with no gummy oil in it, before you fiddle with the high speeds. I guess the summary is "mess with it at your peril".

Cheers,
Dez

[Highway 61]

Originally Posted by Dez

You can also reduce the tension by turning the screw in the opposite direction, but you need to push the little spring catch out of the way to do it. This is much easier if you first remove the shutter cover- easier than it looks. One frustrating thing about Contax shutters though is that there is not a separate tension control for the two curtains- that screw works on a common spring. Shutter speed is determined primarily by the slit width, which is a function of the two curtain releases under the top cover. Getting the high speeds right is difficult, made worse by the rather dubious design which has much of the film wind train also operate when the shutter fires. Any drag in this gear train will make the high speeds unusable. The gear train must be in perfect shape, with no gummy oil in it, before you fiddle with the high speeds. I guess the summary is "mess with it at your peril".

Cheers,
Dez

You are speaking of the prewar Contax shutter here no doubt, and the OP's question was about a postwar Contax shutter.

On the postwar Contax it's fully impossible to get access to the shutter box without completely dissassembling the camera and pulling the shutter and rangefinder units altogether off the main camera casting.

The only adjustment which is possible on the postwar Contax without taking anything apart but one cover screw is to increase the shutter tension, at the risk of immediatly overtensioning it and making the shutter capping problem worse than before - to solve the shutter capping problems, the key is not with shutter tensioning but with corrosion and grime inside the shutter rollers sealed shafts.

[Dez]

Yes, thanks for clarifying. It is easier to get at the mechanism on the prewar ones. I have a IIA at the moment that remains capped at the highest shutter speed, and I have been putting off taking it apart to clean out the gear train. It's almost as if it had been specifically designed to be difficult to service.

Cheers,
Dez

[Crazy Fedya]

Thanks everybody for your answers. I was able to take my IIIa apart and relieve curtain tension. Now it works like a charm.

Originally Posted by Dez

Yes, thanks for clarifying. It is easier to get at the mechanism on the prewar ones. I have a IIA at the moment that remains capped at the highest shutter speed, and I have been putting off taking it apart to clean out the gear train. It's almost as if it had been specifically designed to be difficult to service.

Cheers,
Dez

Actually, it is not all that difficult. It just seems that way

[sevo]

Originally Posted by Dez

I have a IIA at the moment that remains capped at the highest shutter speed, and I have been putting off taking it apart to clean out the gear train.

So have I. But the general consensus seems to be to better leave them that way as long as they are accurate down to 1/250 and have a still usable (but perhaps marginal) 1/500 - fiddling with the top speed tends to compromise the overall shutter accuracy for the questionable benefit of one extra speed with known reliability issues.