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01-07-2011, 03:18 PM   #1
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SMC Pentax-A f/2.8 photos blurry on left side

I got this lens on ebay (SMC Pentax-A 28mm f/2.8) for a decent price. It looks like it's in great shape, but the photos become blurred on the left side, no matter how far I step it down. Here are some images:

f/2.8


f/16


Has anyone encountered this before? I need to decide if I'm going to try to return the lens, or if I'm going to see if it is repairable.

Thank you.


Last edited by Designosophy; 01-07-2011 at 03:19 PM. Reason: forgot to mention focal length
01-07-2011, 03:43 PM   #2
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Most likely, it is decentered... I'm afraid the cost of having it fixed would exceed the cost of a 'new' one. If you can return it, do it right away.

Last edited by causey; 01-07-2011 at 03:52 PM.
01-07-2011, 03:48 PM   #3
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That's not good It looks really badly decentred.
01-07-2011, 03:51 PM   #4
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The lens probably had a shock. Hence the decentering.

01-07-2011, 04:12 PM   #5
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It could also be that the lens was taken apart and not put back together properly. That lens is fairly easy to get apart if you want to tackle it. Most likely bet is that the front element is mis-seated (if that's the case).

01-07-2011, 04:58 PM   #6
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Thank you for the responses. I have contacted the seller regarding the issue. Let's see how he responds. If I end up unsatisfied, I may try the take-apart suggestion, though it scares me badly.

An interesting aside: If I shake the lens lightly, the front element seems to rattle around. If I shake it while holding the metal ring around the front element, the shaking stops.

Last edited by Designosophy; 01-07-2011 at 05:08 PM. Reason: Additional information
01-07-2011, 05:10 PM   #7
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It seems you identified a symptom of the problem.
01-07-2011, 05:16 PM   #8
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QuoteOriginally posted by Designosophy Quote
Thank you for the responses. I have contacted the seller regarding the issue. Let's see how he responds. If I end up unsatisfied, I may try the take-apart suggestion, though it scares me badly.

An interesting aside: If I shake the lens lightly, the front element seems to rattle around. If I shake it while holding the metal ring around the front element, the shaking stops.
I've had one of these lenses with a loose front lens group. It's in a threaded carrier. You can probably screw it back in with finger pressure.

01-07-2011, 05:37 PM   #9
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QuoteOriginally posted by Just1MoreDave Quote
I've had one of these lenses with a loose front lens group. It's in a threaded carrier. You can probably screw it back in with finger pressure.
Hallelujah! I think this solved the problem. What a relief. This is the closest thing I have on hand to graph paper, and the edge softness at f/2.8 seems to be within the acceptable range.



Yes, it's definitely solved. What a huge relief!

Last edited by Designosophy; 01-07-2011 at 05:46 PM. Reason: Additional info.
01-07-2011, 07:20 PM   #10
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QuoteOriginally posted by Designosophy Quote
Hallelujah! I think this solved the problem. What a relief. This is the closest thing I have on hand to graph paper, and the edge softness at f/2.8 seems to be within the acceptable range.



Yes, it's definitely solved. What a huge relief!
I've had more than one of these lenses like that. Glad it's not a big problem anymore for you.

01-08-2011, 08:27 AM   #11
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Thanks again for all your help. This is the second time that forum members have helped me get out of a bind in the past few months. If I hadn't lost my job recently, I'd be making a donation to the forum at this point. And I might, just the same...
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