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04-05-2011, 06:46 PM   #1
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Slow Diaphragm Blades on K 28mm f3.5

Hey guys, the diaphragm blades on my K28 f3.5 are a bit slow. I took the mount off to see what's the matter, and to me it seems like the ring with the aperture lever is rubbing again the mount at some point. When I take off the mount everything seems to be pretty good. I've read somewhere recently that K series lenses tend to develop this problem, so I was wondering if any of you've guys found a way to solve this issue.

I tried applying some lube, which didn't seem to help. Also tightened all the screws to make sure they don't stick out. The lens now works much better than when I bought it, like I couldn't even use it at f8 because the blades were too slow. But I think I can now crank it up all the way to f16. However, f22 seems to be a bit too slow. I don't want to start sanding things off just yet to make sure I don't mess it up. Any tips? Thanks.

04-05-2011, 06:57 PM   #2
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Original Poster
I have just taken a look inside my 55mm f.18 and noticed there is a little plastic piece separating the mount from the ring, I wonder if Asahi became aware of the problem and this was their fix, or if that plastic piece is for something else entirely.
04-06-2011, 03:57 AM   #3
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Location: Kiruna, Sweden
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I have had a similar problem with a K-lens, I fixed the problem by cleaning the ring all together. Once the ring an all surrounding surfaces were clean, the aperture worked perfectly.

04-06-2011, 04:24 PM   #4
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Ok, I guess I'll try it. I think the lens is now closing to f22 on time but when I move the lever I still sort of feel the resistance of something rubbing. My other K's don't show this problem. Oh well, thanks for the advice.


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