Inconsistent focus with SEL20F28, help!

Started 4 months ago | Discussions thread
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AHM
AHM
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Inconsistent focus with SEL20F28, help!
4 months ago

Sorry, this is a continuation of a previous thread on how to avoid camera shake. My problem is that with my new SEL20F28 I get many unsharp pictures. I first thought it was due to camera shake due to lack of OSS (hence the other thread), but now I have realize that is not the problem. So, I wanted to put a new thread with a different subject line.

I did the following experiment: I put the camera on a tripod. I set AF-A, small flexible spot center. The flexible spot is on the red line on the first box. The I just repeatedly took pictures of these (boring) boxes. Look, picture 1,2 are in focus (kind of, at least), but then picture 3 is completely out of focus, and then picture 4 is back in focus. EXACTLY same setup in each picture! This is not only for this scene. I have tried (see the other thread) to take random pictures, and around 20% are inexplicably out of focus.

Do you agree that the lens has a problem (none of my other lenses have this problem, so it's not the camera)? The issue is I bought from eBay with no return, so I think I need to prove that the lens is defective, and then perhaps I can use eBay's money back guarantee? I never bought anything used from eBay before, so I'm not sure what are my options.

First picture, in focus

Second picture, in focus

Third picture, out of focus

Fourth picture, in focus again

 AHM's gear list:AHM's gear list
Sony a6000 Sony E 55-210mm F4.5-6.3 OSS Sony E 16-50mm F3.5-5.6 PZ OSS Sony E 35mm F1.8 OSS Samyang 12mm 1:2.0 NCS CS
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