Pentax 16-50mm f2.8 woes

Started Oct 11, 2017 | Questions thread
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Phil_Rose Contributing Member • Posts: 934
Pentax 16-50mm f2.8 woes

Hi all, I just bought a used lens (16-50) on ebay and I'm finding I have some focusing issues and I don't know if I'm being a pixel peeper or if I need to return it. If I zoom in to 50mm and manual focus then pull out it loses focus. I thought a rule of lenses was that you zoom in to get critical focus then pull back out and you should ensure perfect focus that way but this one goes out of focus.

Secondly and more importantly, it seems to frequently (though not always) focus just a little behind where it loks like it s focusing. This is only in AF mode. It seems worse one people and leaves and better on highly textures objects. I have had an f4 version of the same lens for 10 years or more and I never saw this issue. Is this something others have seen? Is it just that at 50mm and 2.8 it's hard for a lens to be accurate? Surely it's not too much to ask!

Should I return this as having problems? Oh, and when I zoom in the extended part of the lens 'jiggles' a little. Should it be firm in its casing?

Thanks for any thoughts!


PS the cats shot here were done with this lens and they seem OK but then I shoot this image and I focussed on the fluffy seed thing and it's the hairy stuff in back that it's focused on!

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