Aperture wont open properly, Olympus Zuiko 50mm 1.8

[Rob OM]

Goodday,

On my Olympus Zuiko 50mm 1.8 the aperture won't fully open after being closed manually. Closing the aperture feels heavier (more resistance) then on my other lenses.
What could possibly cause this issue and more importantly is there anything I can do about it?

Rob

 

[Richard S. (rich815)]

Time for a CLA.

 

[MattKing]

I've seen sticky apertures on a couple of Zuiko 50mm f/1.8 lenses. They may need to be cleaned and adjusted every quarter-century or so.

 

[David Lyga]

This is really easy to fix if the problem is a bit of oil on the aperture blades. But, then again, I have done this for years.

I would unscrew the front logo ring, then remove the front element set to get at the front of the blades. (miniature screwdrivers to remove screws). Then I would unscrew the rear element set (pliers) to get at the back of the aperture blades. Then I would carefully open and close the blades to see where the oil is. Remove most with soft, clean tissue. Most of the time the oil becomes buried under blades. A bit of lighter fluid can help here: impregnate some clean tissue and rub gently. It will take patience to get it all and you are not done until your tissue remains clean after rubbing. Opening and closing the blades (with the lever on back of the lens) will help to expose more grease to get rid of. If the blades are wet from the lighter fluid, use a hair dryer to get it dry. The blades should spring open and closed rapidly if there is not resistance. Remember, that at room temperature the springiness is better than if the lens were very cold. You must remove ALL grease because when you use that lens in extreme cold you want the same aperture rapidity.

The problem of grease on the blades comes from the lens being stored (even for an hour!) in an extremely hot environment like a car's glove compartment in the summer. The grease from the focus helicoid turns liquid and drips onto the blades. - David Lyga

 

[EdSawyer]

Take the rear mount off and actuate the lever manually. See if that helps. Most issues like this I have seen on OM Zuikos is a dent or bent item in the mount, where the levers that actuate the aperture are. rarely if ever has it actually been oily blades or anything like that.

 

[David Lyga]

Yes, Ed brings up a valid point that I omitted. I COULD be the lever mechanism rubbing against something that is preventing a rapid closure. The rear mount's (4 or 5) Phillips screws are flush with the flat rear mount surface. But, yes, it also could be oil on the blades and that is not as rare as one would think. - David Lyga

 

[E. von Hoegh]

Take the rear mount off and actuate the lever manually. See if that helps. Most issues like this I have seen on OM Zuikos is a dent or bent item in the mount, where the levers that actuate the aperture are. rarely if ever has it actually been oily blades or anything like that.

Don't take the mount off yet. There are two levers, one which moves with the aperture ring, and one which provides the auto aperture function. It's the second one that has to be free, set the lens at minimum aperure and see if the second lever moves freely, and the spring returns it smartly. Then, if it's sticky, you can go on to find out why. I say leave the mount on, because it could be rubbing against the mount.

 

[Rob OM]

Thanks a lot for these quick responses, I will give it a try when I have some more time on my hands.

 

[HTF III]

If you are going to get out the cheap Family Dollar screwdriver set, use a 50mm lens turned-around-backwards as a magnifier, and file your cheap screwdrivers to fit the screw slots perfectly, so you don't end up with a knucklehead job of it. Nothing worse than chewed-up screws from where some clown ruined it (no insult intended). GL

 

[John Koehrer]

In a former life repairing photo stuff, the Oly 1.8's with slow aperture was usually oil on the linkages accessible by removing the mount.