frank_oddsocks Posted October 18, 2003 Share Posted October 18, 2003 I have a 28/2.8 which has developed a slow aperture. That is, it often takes a 1/2 second or so to open up after being closed down. I can't see any oil on the blades. Since the iris is normally stopped down (as opposed to the spring working to stop down, as with Nikon and Mamiya) it seems to me that exposure should still be correct so long as I don't use a motor drive. But I'm worried about stressing the linkage in the camera body and am afraid to use the lens. It does feel rough if you work it off the camera. Any thoughts? By the way, this is the second 28/2.8 to die on me. Are they weak by nature, or is it just that they tend to have been abused by previous owners? Link to comment Share on other sites More sharing options...
frank_oddsocks Posted October 18, 2003 Author Share Posted October 18, 2003 Whoops, should read "normally opened up". Link to comment Share on other sites More sharing options...
fernando_gonzalez_gentile Posted October 18, 2003 Share Posted October 18, 2003 Though it seems as if it were a weak design, nothing wrong with mine since 1981. They might have been abused I think. It surely isn't dead, just repair it. And it's quite a fine lens. Good luck, Fernando. Link to comment Share on other sites More sharing options...
lex_jenkins Posted October 18, 2003 Share Posted October 18, 2003 I noticed after dropping my 50/1.8 Zuiko the diaphragm became sluggish. After disassembling it I discovered a tiny ding that interfered with the auto diaphragm actuating levers. The repair was easy. OTOH, I don't trust a lens that's been dropped. Optical elements may become decentered and hinder performance. The 50/1.8 is common and cheap enough that replacement makes more sense than repair. It's possible that the spring connected to the auto diaphragm linkage has weakened. The Zuiko, like the Minolta, Pentax, Nikon and other mounts, didn't use the strongest auto diaphragm mechanism - that honor goes to the Canon FD design with its dual springs and strong leverage system which enable even an oily diaphragm to operate almost flawlessly. If you decide to tackle the repair don't use any lube. Just clean the diaphragm linkage (arms, spring, etc.) with a cotton swab moistened in Ronsonol/naptha. Watch out for tiny loose bits. Don't try to disassemble the lens beyond the rear mount - Zuikos can be a bitch to disassemble and reassemble correctly, especially the alignment of the focusing helicoid. Link to comment Share on other sites More sharing options...
stephen hazelton Posted October 19, 2003 Share Posted October 19, 2003 I've got a 200mm f/4 vivitar lens that has a similar problem- when you take a shot, it takes maybe 1/10 of a second or less to close down- but that means any short exposure will be way over exposed. My solution (which I haven't tried yet!) will be to take the diagonal cutters to it, clip off the little lug that triggers the aperture (this is a Pentax K mount, by the way). If I understand it right, I'll have stop-down metering and be on my way. If I guess wrong, I'm out the $20 I spent on the lens. Good luck on yours! Link to comment Share on other sites More sharing options...
thom_english Posted October 19, 2003 Share Posted October 19, 2003 I have a 28/2.8 that is acting similar to that. It is a lens that I bought used several years ago and have used alot. Mine is slow to open but it is not rough. I still use it, I am just careful when I meter with it to be sure it is not still stopped down. Probably is repairable, but why spend the $$ if you do not have to. Link to comment Share on other sites More sharing options...
lars_arvid_s. Posted October 19, 2003 Share Posted October 19, 2003 After I dropped my 28/2,8 about 2 meter down it developed the same symptoms, but I don't consider this a fatal fault, and I still use it just as much as before. If it stops working, it stops working, nothing to be bothered with until then, as long as the optical performance is still fine. HTH, Link to comment Share on other sites More sharing options...
frank_oddsocks Posted October 20, 2003 Author Share Posted October 20, 2003 Thank you for your responses. It seems that i) it is a relatively common problem caused by mechanical damage ii) the repair is cheap and iii) there are plenty of people who would buy the lens knowing about the problem. I didn't drop this lens but it has been subject to vibration. <p> Thom wrote: <i>Probably is repairable, but why spend the $$ if you do not have to.</i> and Lars wrote: <i> and I still use it just as much as before. If it stops working, it stops working, nothing to be bothered with until then, as long as the optical performance is still fine. </i> It's a A$100 repair on a lens that might damage an A$1500 OM-3. I can't verify the optical performance without spending A$20 on film and A$10 on processing. But I guess some people save money too by never topping up the oil in their car engine. <p> By the way, the diaphragms on my Pentax 67 lenses are lighter, smoother and faster than any Zuiko I have ever seen. Link to comment Share on other sites More sharing options...
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