OM Zuiko 50mm 1.8 not stopping down

Kyle M. · Feb 15, 2014

The other day a friend of mine gave me a black Olympus OM-1 with Zuiko 50mm 1.8. Checking it out today I noticed that the lens does not stop down either when hitting the dof preview button, or when pressing the lever on the rear of the lens. Sometimes it will stop down but slip back open while I am holding the dof preview button in or flicking the lever triggered by the body. Anyone know if this is something I may be able to fix myself, or should I just look for another lens. The body on the other hand is excellant and the shutter speeds sound good.

mopar_guy · Feb 15, 2014

John Hermanson would overhaul this lens for a reasonable price:

http://zuiko.com/index_010.htm

gone · Feb 15, 2014

It sounds like the aperture blades are sticking. Probably has old oil on them. If you're familiar w/ opening lenses and cleaning the aperture blades it is probably not that hard of a job. If you don't do much of that, it may be better to look for another lens, or have the repair guy mentioned in the previous post give you an estimate. A quick look on ebay shows them going for $20 to $30, so replacing it may be cheaper than sending it out. That's usually the case.

pen s · Feb 15, 2014

Well, a replacement used lens from KEH, bargain grade (their bargain grade is better than most other dealers EX grade) is $29+shipping. That gives you a baseline price. If it were my lens and I felt handy I'd disassemble it to the point that I could flush the aperture and if I couldn't fix it I'd just buy a used one. Newer ones might be optically better than older ones but they seem more cheaply built to me. I have a very early one from 1973 and it still has fast and free aperture function.

My 2 cents from living with OM lenses and bodies for 40 years.

nsurit · Feb 15, 2014

I'll mail you a good one without sticky aperture blades for $25 in the USA. Bill Barber

Kyle M. · Feb 16, 2014

Well considering that I'm fairly mechanically inclined I decided to remove the mount end of the lens and have a peek inside. Being that finesse isn't one of my fine points I managed to spill all the lenses guts out on my workbench, and got to fiddle about trying to figure out how exactly everything worked together. The good new is that my lens is back together and working perfectly, the aperture blades look to be oil free and are snappy at all settings and the DOF preview button even works. Now all I have to do is wait for daylight tomorrow to go shoot a test roll of Tri-X.

nsurit · Feb 16, 2014

Might you share with us what you did to it once it was apart and spread all over your work bench?

Kyle M. · Feb 16, 2014

Inside the rear of the lens are two rings that control the aperture, one is connected via a prong extending down into the lens and moves with the aperture ring. The other goes through a small plate that moves the aperture blades. These two rings appear to have been installed upside down at some point in the past and the prongs facing down were supposed to face up. I believe that the way they were installed had the shorter prongs extending down and they were not long enough to engage the aperture control. Allowing them to some time catch and stop the lens all or part of the way down, and then slip because they were just barely touching.

OM Zuiko 50mm 1.8 not stopping down

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