vivitar lens diaphragm

[easilyamused]

Hi,

I'm brand new to the Photo Forum and almost as new to photography besides point-and-shoot! As I've been getting into taking pictures, I've dusted off an old Konica Autoreflex TC that once belonged to my great uncle. Among the lenses that dear Uncle Hymie had for the camera is a Vivitar 70-150mm f/3.8. When I use the lens on the Autoreflex in autoexposure mode, the diaphragm will stop down as the exposure is made but then refuses to open back up afterwards, so my viewfinder stays dim. The only way to get it back open is to take the lens off the camera! Everything works properly in manual mode, and the other (Konica Hexanon) lenses I have work fine too.

Is something wrong with the Vivitar? Or is it maybe just incompletely compatible with the Konica?

 

[Early]

You probably have lubricant leakage on the diaphragm blades. If you can't take the lens apart and clean them yourself, either use the lens wide open or throw it away. It's not worth the cost to have it professionally cleaned.

 

[cooltouch]

You can examine the blades for oil residue by moving the lens stop down lever at the back of the lens. Set it to f/16 or so, flip the lever, and take a look.

Also, if this is your problem, you should expect to see the diaphragm stick closed when you actuate it. If the diaphragm operates as it should, and there is no sign of oil on the blades, then the problem may lie with the camera.

I am not familiar at all with Konica, but there should be some sort of lever or arm inside the lens mount that actuates the lens diaphragm. When you trip the shutter with the lens off the camera, this arm =probably= should move quickly back and forth (I say probably because, with no lens on the camera, it may behave differently, I just don't know). If it moves in one direction and stays there, this might just be your culprit.

 

[Dwig]

You probably have lubricant leakage on the diaphragm blades. If you can't take the lens apart and clean them yourself, either use the lens wide open or throw it away. It's not worth the cost to have it professionally cleaned.

It could also be some other stiffness in the diaphram linkage (dirt, grit, stiffened lubricants) that make reopening the iris take more force than it should. If this happens, the body can easily let the iris close, trapping it at the correct f/stop, but not have the strength to reopen it. Properly working lenses (your other lenses) open easily enough and the body has no difficulty with them.

Regardless of the cause, it is probably not worth the expense to have the old Vivitar fixed.

 

[easilyamused]

Thanks for all the responses! You're all right that the lens isn't worth troubling over too much, but it's valuable for me to hear your diagnoses so I can learn more about lenses, how they work, and what can go wrong.

The diaphragm opens and closes smoothly and with no apparent stiffness when I move the lever with my hand (when it's not connected to the camera), but on the other hand, the camera has no trouble operating the Hexanon lenses I have, so I'm not sure where the problem lies. Probably I'll just use the zoom in metered manual if I can't figure it out.

If anyone else has suggestions, I'd love to hear them as well, if only for my own education.

 

[Derrel]

Can you just take the lens off the camera, and manually actuate the diaphragm a few dozen times? My guess is that the lubricant has stiffened,and that after maybe a hundred actuations, the diaphragm might come "unstuck".
I would try manually actuating it for 15 or 20 minutes,and see if that helps.