[Phalbert]

Hi everyone. This is my first post so it's possible that my subject has already been discussed but I couldn't find the right answer in this forum. My question is in the title. I wish to make the lens completely manual but the aperture ring has been "modified" already and the aperture is pulled back to 16 by a spring. You can move the aperture but the moment you leave it it goes back to 16. Not very practical. My version of the lens is the shiny aluminium one. I'll try to add a pic. Thanks for any input.

Attached Images

View Picture EXIF

File Date

 

[stevebrot]

Welcome to the Pentax Forums!

Is it safe to assume this lens is M42 screw mount? The location of the aperture ring at the front is usually an indication of a full manual aperture or some sort of preset aperture mechanism. It would help to have photos from the rear (cap off) and from the front and any view that might show a special lever or switch or button.

Edit: See follow-up post below...


Steve

[stevebrot]

I think I may have found your lens...CZJ 50/2.8 Tessar, Semi-Auto diaphragm?

If so, this previous thread describes a similar problem and might be helpful...

carl zeiss jena tessar 50mm f2.8 problem - PentaxForums.com

Below is a quote form another forum. I would have linked directly to the post but could not figure out how...

It seems the Carl Zeiss Jena 50mm f2.8 Tessar lens was produced for so many various camera mounts (Exacta, Werra, Pentina, Pentacon). The Praktica FX3 version has an M42 screw mount. This Praktica version has a quirky semi-automatic aperture mechanism that had me baffled at first, which made me think the aperture ring was busted. The aperture ring has to be pulled (towards the camera body) before the setting can be changed. When mounted on the FX3, the aperture ring also has to be turned clockwise to "cock" the spring-loaded aperture in the full-open position so that a bright image can be seen on the focusing screen (without a pentaprism).

Source: Carl Zeiss Jena Tessar 50mm 1:2.8 - NEX-5N | TalkEmount

I think this might solve your problem.



Steve