Konica III one aperture blade stops at F2.8

[bdeyes]

Another Konica III quirk:
I just noticed that on my Konica III with Hexanon F2.0 lens (with leaf shutter), that one aperture blade (of 5) refuses to open up further beyond F2.8. So if I set the aperture ring to F2.0, the mis-behaving blade sticks out a bit, and the aperture has a crescent-moon shape. Obviously at F2 this will have an impact on the image as one side of the image will receive more light than the other. At other apertures F2.8 and smaller, this blade does behave a lot better, but still not perfect. As I move towards smaller apertures, the opening gets progressively smaller, but the opening is tear-shaped, not a pentagon as I suspect it should be.

Any idea what could be the problem? I read about how dried oil can gum up the works, but I can't see how it would affect only the one blade at the large aperture. Could this be an issue with a spring for this blade?

I could resign myself to shoot only at F2.8 and smaller, but it would nag me no end not to be able to use this excellent camera at its fullest potential. Also, has anyone tried taking apart the lens assembly on the Konica III before? Because it has its film wind lever on the side of the lens barrel, I wasn't sure how could complicate the dis-assembly / re-assembly steps.

Thanks a bunch!

 

[Ranchu]

I've cleaned a few sticky shutters, it may only need something like that. If the blade is out of place in it's mechanism, that's not something I would attempt to do myself. The aperture mechanism is usually about as far in as you can go (everything taken apart). Might be a good idea to search out a good tech, and ask to have it cleaned if that's all it needs or repaired if not. It's such a nice camera, it could probably use a little TLC at this point anyway.

 

[Ranchu]

On the bright side, your lens will be sharper at 2.8, and I'm not sure that an aperture that is an off center oval will lead to uneven coverage. Most all point and shoots use a combined aperture/shutter made of two L shaped blades that make a lopsided diamond shape, it doesn't seem to lead to that...

 

[ZeissFan]

You'll need to remove the shutter and then the back of the shutter to get to the aperture blades. They're off their track. Reseating them is an exercise in patience -- figure at least 20 minutes.

 

[bdeyes]

I tried getting to the blade, and got so far as the shutter the cocking ring. Where I must have damaged one of the springs for the shutter. Now not only am I limited to F2.8, I am also limited to shutter speeds 1/25 to 1/500. Which isn't so bad, but I know when to fold.

I'll live with the camera, as a custom F2.8 lens, for daylight shooting only.

Appreciate all your guidance though.