radiojohn

In a moment of nostalgic weakness, I won an auction for a 1970's Praktica [rebadged Cavalier STL-1] with the Oreston lens. When I press the pin on the lens back or the rectangular button on the side of the lens, nothing happens, the lens does not stop down. The button on the side doesn't even depress as it should.

I suspect the problem is with the button jamming something. Has anyone else dealt with this? The lens screws show no sign of tampering.

MrPhotog

What aperture do you have the lens set to? If you have it set wide open, pushing the pin does nothing. Set it to f/11 or f/16 and see if you still get no diaphragm movement.

With older lenses there is an excellent possibility that someone opened them to clean them before selling them, and may not have reassembled them properly.

if the aperture isn't working, and that was not disclosed in the auction, return the lens quickly.

radiojohn

Thanks for the suggestions. I'm pretty familiar with M42 lenses, so I did check at all apertures. This was a thrift-store purchase, so I suspect it is a mechanical failure.

imagemeister Loc: mid east Florida

That is why it was in a thrift store .....I have seen many lenses with non working diaphrams - for no good reason . In most, the lubricant vaporizes and condenses on the diaphram blades from a high heat exposure.

radiojohn

Sounds reasonable.

AnnH

I have one of these and haven't played with it a lot but this post reminded me of the trouble I had figuring it out. I have the exacta mount with a Nikon z6 camera. When you you change the aperture you don't see the diameter of the aperture change, I thought my lens was defective. I noticed when I pressed a square button on a ring under my aperture ring the diaphragm changed. After some research I read that it will stay wide open no matter your setting until you press that square button and hold it down while taking the picture. Its rather awkward but does work. I hope the photos are fantastic because I find it quite awkward. And I have very small hands!

radiojohn

On the thread mount, the in the back is supposed to close the blades and the square button is for older cameras, Zenits or bellows. I have just three big screws on the back, so I may take a peek inside.