HB Zeiss 80mm planar: aperture leaves move slowly when stopping down

[ChrisBCS]

First let me say, Aperture closes to proper size instantly during exposures. Tested using bulb shutter speed to observe.

However, with the shutter cocked and set to say, f22, if the stop-down catch is depressed, the leaves will close slowly and not at a constant pace (speed up, slow down, etc. during the stop down). They will, despite this motion, close to the proper aperture size. Is this normal or a sign of problems to come?

 

[John Koehrer]

Hi,
It is a sign of the future.. As much as I don't like the term, it'll benefit from a CLA.

It's odd that it'll work normally on B but not at a set speed. Check out the body by
removing the lens and do the same checks while you watch the cocking/release shaft
as it rotates to see if you get the same result. If it seems to work, put a little pressure
on it with your finger to see if it slows down.

You can check the lens when it's off the camera by using the release lever
next to the shaft on the back of the lens

 

[Sirius Glass]

Time for a CLA.

 

[ChrisBCS]

When I took the lens off the body and pressed the stop down catch I got the same result as on-body, slow jerky moving, but it is gradually increasing speed with use of the catch. When I manually fired the shutter using the release lever on bulb, it instantly stopped to f22, again just as before. However, after manually cocking the shutter off-body, I can't get the step down to misbehave again. It functioned perfectly off-body after being cocked.

After being placed on the body again, it does misbehave a little on the stop down. But, as I mentioned above, the movement after depressing the stop down catch has been getting faster and faster with each repetition. I wonder if lack of use of the lens has anything to do with it? It's from 1975 and purchased from KEH looking practically NIB (though they didn't grade it that high), so it may have been sitting in a box since 1982.

Many thanks.

 

[ChrisBCS]

I leave the digital work for the urologists and proctologists.

Thank you for this.

 

[Sirius Glass]

Feel free to quote me at no charge.

 

[ChrisBCS]

After several manual stop down cycles from 4 to 22, I cannot get the malfunction to occur again. At least for the moment...

 

[RalphLambrecht]

After several manual stop down cycles from 4 to 22, I cannot get the malfunction to occur again. At least for the moment...

I think you nailed it. lack of use can cause hardening of lubricants and repetitious cycles can free it up; still would consider a CLA. I work all my lenses and bodies once a quarter through all speeds back and forth to keep things moving;underused shelf-queens will eventually fail.

 

[Theo Sulphate]

... lack of use can cause hardening of lubricants and repetitious cycles can free it up; still would consider a CLA. I work all my lenses and bodies once a quarter through all speeds back and forth to keep things moving;underused shelf-queens will eventually fail.

Yep. Lack of use is not good.

One thing I do to test old lenses I find is to set the aperture to its minimum (e.g. f/16) and shutter speed to its fastest (e.g. 1/1000), then trip the shutter while looking through the back of the camera. All that should be visible is that small aperture. If it's large, that means the blades aren't closing fast enough at the time of exposure.

 

[Sirius Glass]

I agree. Time for a CLA before something breaks.

 

[AgX]

After several manual stop down cycles from 4 to 22, I cannot get the malfunction to occur again. At least for the moment...

I common experience to all who have a lot of old lenses. Just this week I brought home a lens not closing beyond 5.6 and "repaired" it by acftuating the automati diaphragm a hundred times.
But likely that stickiness will return, though nobody knows when... With such lens it is at least advisable to check the automatic aperture function before use. And sooner or later the lens should be disassembled and the diaphragm assembly should be cleaned.