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08-01-2011, 06:23 AM   #1
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lens aperture lever sticks...

I've a problem that's similar to earlier threads regarding sticky levers, but I found that this one was the lens, not in the camera body.

The lens with the issue is an smc M 50 1.4. Same prob happens - even if I adjust the aperture ring, all the shots look the same. I'm sure it's the lens because when I swap it with another lens with an aperture ring, it works on the other lens.

What could the problem be? And could it be solved in a DIY manner or should I take it to a repair shop? I'm quite a newbie with lens troubles so I'm pretty clueless... Help or tips are highly appreciated. Thanks in advance!

08-01-2011, 06:47 AM   #2
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I'm really not qualified to answer your question, but I'm interested in the answers. I have a very nice K55/1.8 that has a sticky aperture. The blades look perfectly clean and dry, but the lever seems to jam in a not-quite-open position. At times I can jiggle the lever and get the lense to open up and to stop down to where it's set, but sometimes it just doesn't want to go. I've also noticed that I can hit the optical preview a few times and get it to free up sometimes while it's on the camera. This doesn't always work.
08-01-2011, 08:52 AM - 1 Like   #3
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With the lens off the camera, you should be able to turn the aperture ring and see all 8 blades form a tiny octagon at f22. then gradually make a larger ocagon until disappearing at f1.4. If that works, go back to f22, then flick the aperture lever on the mount. The blades should rapidly open fully and snap shut when the lever is released.

If those tests don't work, something is wrong with the lens. If they do work, it's some kind of problem with the camera/lens combination, like a bent lever.
08-01-2011, 03:53 PM   #4
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QuoteOriginally posted by Just1MoreDave Quote
With the lens off the camera, you should be able to turn the aperture ring and see all 8 blades form a tiny octagon at f22. then gradually make a larger ocagon until disappearing at f1.4. If that works, go back to f22, then flick the aperture lever on the mount. The blades should rapidly open fully and snap shut when the lever is released.

If those tests don't work, something is wrong with the lens. If they do work, it's some kind of problem with the camera/lens combination, like a bent lever.
The lens blades do flick open and snap when I release the lever, but when it comes to the bottom of the space, it sticks there... It locks up at around f/2 and f/1.4. Hopefully there's nothing broken in the camera body, will check again later. Thanks a lot sir! I'll follow up as soon as I check.

08-01-2011, 08:02 PM - 1 Like   #5
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QuoteOriginally posted by Alizarine Quote
The lens blades do flick open and snap when I release the lever, but when it comes to the bottom of the space, it sticks there... It locks up at around f/2 and f/1.4. Hopefully there's nothing broken in the camera body, will check again later. Thanks a lot sir! I'll follow up as soon as I check.
Your aperture blades are starting to stick, the only real solution would be to take the lens apart and degrease the aperture blades. You might try to work the lever a lot and see if that makes any difference or apply some heat to the lens (a hair dryer will do) and see if that will free up the diaphragm. If heating up the lens works, then sooner or later you will have to degrease the diaphragm.

Hope this helps,
08-03-2011, 10:20 PM   #6
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QuoteOriginally posted by excanonfd Quote
Your aperture blades are starting to stick, the only real solution would be to take the lens apart and degrease the aperture blades. You might try to work the lever a lot and see if that makes any difference or apply some heat to the lens (a hair dryer will do) and see if that will free up the diaphragm. If heating up the lens works, then sooner or later you will have to degrease the diaphragm.

Hope this helps,
Thanks for that tip! I'll try that later.
08-04-2011, 10:18 PM   #7
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There are 3 possible reasons:

1) The rear lever is bent outward and jammed when mounted on the camera, but unlikely because it should not stick when unmounted.

2) Greasy aperture blades.

3) The piece of round shape metal that the rear lever sits on is bent inside the lens. This can happen if the lens was serviced before. It takes very slight amount of distortion to stick.
08-05-2011, 03:36 AM   #8
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The one thing I didn't see asked or answered in this thread is What mode are you using this lens in? Forgive me if I've missed it somewhere. You Do know these lenses will only work (stop down the aperture) in M mode, Do you not? Point is, make sure of your technique before tearing into the lens itself.



08-07-2011, 09:20 AM   #9
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QuoteOriginally posted by wlachan Quote
There are 3 possible reasons:

1) The rear lever is bent outward and jammed when mounted on the camera, but unlikely because it should not stick when unmounted.

2) Greasy aperture blades.

3) The piece of round shape metal that the rear lever sits on is bent inside the lens. This can happen if the lens was serviced before. It takes very slight amount of distortion to stick.
Still sticks when unmounted And I do think this was serviced before...for cleaning I think.

pics of the lens...




the white arrow indicates where it usually was when I move the aperture ring. When I try to move the lever manually, it sticks to the bottom...
note that the lever is in a position where it usually should be when at f/1.4, but this time I set it to f/5.6 - and the lever clings to the f/1.4 position. Moving it manually (while unmounted) can bring it to its supposed position (white arrow, 2nd pic) at the indicated aperture. Can't do it while mounted though...

QuoteOriginally posted by JeffJS Quote
The one thing I didn't see asked or answered in this thread is What mode are you using this lens in? Forgive me if I've missed it somewhere. You Do know these lenses will only work (stop down the aperture) in M mode, Do you not? Point is, make sure of your technique before tearing into the lens itself.

Yup, I use Manual mode most of the time when I use a non-AF lens... and also for taking videos. While on video mode though, I can see the effect of moving the aperture ring - DOF increases/decreases as well as brightness of course. Which somewhat confuses me more now Can't figure out why the lever sticks when taking photos, but works while on video? Or is the lever not needed when in video mode?

Last edited by Alizarine; 08-07-2011 at 09:23 AM. Reason: added info
08-07-2011, 10:30 AM - 1 Like   #10
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In Video mode, is the change Immediate? Or delayed? when you change the aperture ring..

Set the camera to B. Hold the camera so that the viewfinder is facing a light source and you are looking through the front of the lens. Set the lens to f22, press and hold the shutter release long enough to see if the blades are closing (assuming they were open to begin with).

What Should happen, is when you mount the lens on the camera...

1. The camera pulls the aperture wide open (true for any but M42 lenses).
2. When you stop down meter, the camera lets the aperture snap shut to the set location (f5.6 for instance) and sets the shutter speed according to the meter reading.
3. When you take the picture, again, the camera lets the aperture snap shut to the set location for the photo.

I assume you know that already though.

These lenses are pretty easy to inspect.

1. If the aperture lever does Nothing, something is disconnected. Even if the blades are oily the lever itself should still snap back.
2. Only at f22 will the aperture lever go all the way to the arrow you indicated but moving the aperture lever in the other direction (away from the arrow) should open the blades to f1.4.
3. If the aperture lever Binds, then it is rubbing on something or something is loose inside, or the aperture lever does not engage the aperture.
4. Leaving the aperture lever free to move, you should see the opening change with each click of the aperture ring.

Again, I assume you know that already (just stating all of the above for someone who may not know it).

You should be able to get into this without taking any of the optics apart.

1. Remove the rear mount.
2. Check that the spring on the aperture lever is There, and functioning.
3. Inspect where the aperture lever goes down into the lens body and make sure it actually engages the aperture.
4. Some lenses (don't remember if this one does or not) have a second spring recessed at the aperture mechanism (you should see the other one right on top when you remove the mount). If it's there, make sure it's connected and working properly.
5. With a small flat screwdriver or similar, you should be able to open and close the blades at that location.

08-07-2011, 10:43 AM - 1 Like   #11
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QuoteOriginally posted by Alizarine Quote
the white arrow indicates where it usually was when I move the aperture ring. When I try to move the lever manually, it sticks to the bottom...
note that the lever is in a position where it usually should be when at f/1.4, but this time I set it to f/5.6 - and the lever clings to the f/1.4 position. Moving it manually (while unmounted) can bring it to its supposed position (white arrow, 2nd pic) at the indicated aperture. Can't do it while mounted though...
Sound like the spring that's hooked to the lever mechanism is gone. You can see if there is anything you can do by removing the black rim without removing the whole chrome mount which can be difficult to remove. There are 3 tiny screws on the chrome mount, remove them and see.
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