Slow Diaphragm Blades on K 28mm f3.5

VaSA · 04-05-2011, 06:46 PM

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.

VaSA · 04-05-2011, 06:57 PM

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.

wavecurrent · 04-06-2011, 03:57 AM

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.

Mike

VaSA · 04-06-2011, 04:24 PM

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.

04-05-2011, 06:46 PM	#1
VaSA Senior Member Join Date: Jan 2009 Posts: 173	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.

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Vivitar 28mm F2 aperture blades	zoeybird	Pentax SLR Lens Discussion	38	01-08-2017 04:40 PM
DA 40 Diaphragm Blade Problem?	Colorado CJ	Pentax SLR Lens Discussion	31	12-26-2010 01:40 AM
Slow Aperture blades on my M-28/2.8, how to proceed?	fazer	Pentax SLR Lens Discussion	4	06-09-2010 04:07 AM
Slow AF? Slow TTL? Check 'em batteries!!!	jboyde	Pentax DSLR Discussion	11	04-30-2009 06:41 PM
How to fix sticky/slow blades?	TimB	Pentax SLR Lens Discussion	35	09-22-2008 09:01 AM

04-05-2011, 06:57 PM	#2
VaSA Senior Member Join Date: Jan 2009 Posts: 173 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
wavecurrent Senior Member Join Date: Jul 2007 Posts: 147	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. Mike

04-06-2011, 04:24 PM	#4
VaSA Senior Member Join Date: Jan 2009 Posts: 173 Original Poster	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.