Tamron 150-500mm autofocus inconsistency?

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razorfish Contributing Member • Posts: 826
Tamron 150-500mm autofocus inconsistency?

Hi, I recently acquired this lens and have been testing it out. One issue I've observed is that some images appear to come out not being razor sharp. From reading reviews, I expected a sharp lens, especially in the center, and very consistent AF. Now I'll admit I'm challenging the lens a bit in my own testing, with distant subjects at 500mm. That's the whole point, to see if it holds up. After noticing these slightly blurry images, I began shooting the same subject multiple times, acquiring AF with each image. Observing my results, I have noticed I can usually get one razor sharp image in a series, but the rest will have some blur, a hit rate of 20-25%. That's nowhere near what online reviewers are getting with this. But at least I should have ruled out optical flaws as the cause. Please look at my 100% crop samples below (please view at full size):

500mm 1/1000s f6.7 ISO160

500mm 1/1000s f6.7 ISO160

500mm 1/1000s f6.7 ISO160

500mm 1/1000s f6.7 ISO160

My observation is that #4 has camera shake, so that's kind of what I'd expect with one in four images at this focal length (even though I did shoot at 1/1000s with both IBIS and VC active). #1 and #2 exhibit the slightly oof look that has me worried with this lens though. It could be hard to notice but compared to #3 (which is the only one I'd consider sharp) there is blurring of the painted letters as well as the railings near the top of the ship. With a rather static subject, I can only think of a slight misfocus as the cause of this, but I'm open to suggestions. And if it is misfocus, should I return the lens? Thank you.

 razorfish's gear list:razorfish's gear list
Sony a7R III Sigma 35mm F1.2 DG DN Tamron 70-180mm F2.8 Di III VXD Sony FE 20mm F1.8G Tamron 150-500mm F5-6.7 Di III VC VXD +1 more
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