problem focusing with 70-350mm with UV filter

[AWood]

I have a sony alpha 6000 and have had some really sharp images with my new 70-350mm lens. However when I put a UV filter on the end the images are very poor. I've tried two filters - a cheap one from Amazon and a Hoya one. The Amazon one is very bad, but the sharpness is still affected with the Hoya filter.  I'm mostly using 350mm to shoot birds. With a filter it is unusable. Any thoughts?

[Olaf W.]

It‘s quite common that filters disturb the autofocus. Leave it off or use a clear flter if you want to protect the lens.

[XKAES]

I'd suggest an easy test.

#1 take a shot without the filter in auto or manual focus.  Just make sure the image is sharp -- and the camera is on a tripod, etc.

#2 with the focus locked in place, put each filter on the lens and take the exact same picture -- without any change in the focus!!!

If either of the filters show degradation, get rid of them.  If the images with the filters are still good, the filters are causing an auto-focus problem.  I've never heard of that, but  anything's possible.

[AWood]

2 hours ago, Olaf W. said:

It‘s quite common that filters disturb the autofocus. Leave it off or use a clear flter if you want to protect the lens.

Thanks - using a clear filter is a good idea

[AWood]

2 hours ago, XKAES said:

I'd suggest an easy test.

#1 take a shot without the filter in auto or manual focus.  Just make sure the image is sharp -- and the camera is on a tripod, etc.

#2 with the focus locked in place, put each filter on the lens and take the exact same picture -- without any change in the focus!!!

If either of the filters show degradation, get rid of them.  If the images with the filters are still good, the filters are causing an auto-focus problem.  I've never heard of that, but  anything's possible.

Thanks - I'll give it a go. I've noticed it with manual focus - I can't quite get the image sharp when either filter is on, so it's not just an autofocus thing.

[XKAES]

Two questions.

Does it only happen with that lens?

Why do you think a clear filter would make a difference?  A clear filter has just as much light distorting glass as a UV filter.

[AWood]

On 3/4/2022 at 5:46 PM, XKAES said:

Two questions.

Does it only happen with that lens?

Why do you think a clear filter would make a difference?  A clear filter has just as much light distorting glass as a UV filter.

It wasn't me who suggested that, I agree with you - a clear filter with have the same problem.

I haven't noticed it with my 70-210mm

Edited April 1, 2022 by AWood

[XKAES]

Did you run the tests that I suggested (above)?

What did you discover?

[thebeardedgroundsman]

Have you tried different focussing modes or focus areas? You might find centre focus is better than one of the wider areas. - Just a thought, I don't know...