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04-12-2010, 12:48 AM   #16
axl
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QuoteOriginally posted by little laker Quote
Not a pic, but a sign of oil on the blades is they don't close as fast, or all the way.
I know symptoms like this, but is it visible in any other way?

thanks anyway Stu

04-12-2010, 03:27 AM   #17
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QuoteOriginally posted by axl Quote
I know symptoms like this, but is it visible in any other way?

thanks anyway Stu
You can indeed simply see the oil in the blades. Looks like some fluid on the usually completely dry blades. If one of your lenses has oily blades, it cannot be mistaken!

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04-12-2010, 03:32 AM   #18
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QuoteOriginally posted by jct us101 Quote
I'm also wondering what the oil on the blades can do that is bad for the lens. I guess having anything wet inside a lens would be bad, and that's kind of a dumb question, but I'm just wondering what effects it can possibly have on it.
The "oil" is usually a residue of the grease used to lubricate the aperture mechanics. If the grease liquifies over time (heat or simply decomposition over time), some oil can sseep put of the roller bearings and creep between the actual aperture blades. That will stick the blades together, which are very thin and lightweight. Thuse the thin oil film will be adhesive enough to slow down or fully stop the movement of the aperture blades. Sometimes you will start noticing the effect, when you get overexposed images, as the aperture will not close down to the chosen f-stop during the exposition. In severe cases the blades can get stuck completely.

The oily residue is usually not dangerous to the lens elements, even if it creeps onto the lenses over time. It can be cleaned off there during the same CLA job, which restores the aperture action.

Ben
04-12-2010, 03:50 AM   #19
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Thanks for clarification.
I'd still love to see pic of oily blades just to be sure...
thanks

04-12-2010, 07:40 AM   #20
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QuoteOriginally posted by axl Quote
Thanks for clarification.
I'd still love to see pic of oily blades just to be sure...
thanks
04-12-2010, 08:07 AM   #21
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+1 for Eric Hendrickson. He CLAd my A 50mm F/1.4 and it's good as new.
04-12-2010, 09:18 AM   #22
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I took my Zeiss 135mm M42 apart to clean up some oil on the blades. It was the first time I've taken a lens apart and it wasn't too terrible - but I had a step-by-step guide to follow that I found on the internet somewhere.

You can see the oil a little bit in this shot - it's the darker smudges just past the end of the blades. They did move but were quite sluggish. It's probably not perfect now but certainly much better than before.

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