Please help, am I going crazy, or is this a lens issue

[Harry Woodford]

Hello all, I recently got a Sigma 500mm f4.5 but have noticed a huge issue with focus since I had it. AF just doesn't seem to work properly, both in the viewfinder providing just off shots and the Live view focus just will not even work. It flashes red and stops after racking. I have tested this against my 70-300mm as well as all other lenses and all work fine. I have just taken these images of our local cats in the exact same position, with identical settings, the sigma just seems off to me.

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P.s here are some additional shots that were easy to capture, but didn't seem to have the ability to focus on the subject. Any other lens I've used in these situations worked perfectly fine.

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[hrv]

Have you tried to calibrate the lens to the body using the AF fine tuning options?
See

 

[Harry Woodford]

Have you tried to calibrate the lens to the body using the AF fine tuning options?
See

Hello although I haven't properly calibrated the lens, I did take multiple shots on a static subject whilst changing the af tune in both directions and still haven't had better results.

At one point I thought I had fixed it, I then tried photos on a seagull in flight using all the same settings as k would on any other lens and it still couldn't focus sharply. It would register the bird as the focus point but wouldn't be sharp.

I also still have the issue of it refusing to find focus during live view.

 

[Krümelkraft]

TBH, I don't know if from your posted cat pictures, I don't see any issue.
That waterbird is a difficult situation. Black bird on reflecting water behind grass in backlight - I'd say it's absolutely normal that the AF fails there.
White gulls also are a bit difficult, especially in flight. I mostly get failed shots of gulls in flight with any lens/camera setup.

 

[Harry Woodford]

TBH, I don't know if from your posted cat pictures, I don't see any issue.
That waterbird is a difficult situation. Black bird on reflecting water behind grass in backlight - I'd say it's absolutely normal that the AF fails there.
White gulls also are a bit difficult, especially in flight. I mostly get failed shots of gulls in flight with any lens/camera setup.

The cat pictures I admit are harder to tell the difference, but I feel cropped my smaller lens still has higher detail.

I have also been out again this afternoon to test further, shooting at birds on feeders to test from a static and stable position it still lacks any real sharpness and detail when you zoom in. Although I'm still relatively new to all this I can confidently say my old 400mm f2.8 was beyond sharper even at higher crops.

I also cannot find anywhere anything thay could cause the live view to not even focus, let alone accurately. I think I will be returning this particular lens back tomorrow and then deciding what to go with next. 300mm 2.8 or a move to sony

 

[Len Shepherd]

TBH, I don't know if from your posted cat pictures, I don't see any issue.

I slightly - but only slightly - disagree.
I suspect the first image would have been a little sharper if a shutter speed equivalent to the angle of view or a little faster - at 1/750 on DX.

That waterbird is a difficult situation. Black bird on reflecting water behind grass in backlight - I'd say it's absolutely normal that the AF fails there.

Agreed

White gulls also are a bit difficult, especially in flight. I mostly get failed shots of gulls in flight with any lens/camera setup.

Without knowing where you focussed - the white front of the gull has negligible contrast making this part of the picture area a less than ideal AF subject.

 

[Robert S]

I would like to help however I have no idea what the problem is.
Reminds me of Paul Hogan saving the guy from topping himself by jumping off Sydney Harbour bridge. After receiving a bravery award Hogan said " I don't deserve this. I was holding onto the bridge a lot tighter than I was the bloke trying to jump. "

 

[MrFotoFool]

They look perfectly fine to me (except waterbird, but that is moving and obstructed by reeds, so any lens would have a hard time).

 

[jeffnles1]

What you may be experiencing is the shallower depth of field offered from a 500mm lens than the 300mm lens. Depending on how close you were, even at F6.3, the depth of field on a 500mm can be fractions of an inch to a couple inches until the subject gets pretty far out. The difference I see in your 300mm shots vs. your 500mm shots may well be chalked up to depth of field. Just a thought.
Jeff