Do i have an AF isssue with my Sigma 500? (1 Viewer)

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TobyH

Well-known member

• Jan 12, 2011

• #1

Hi all,

I recently picked up a secondhand Sigma 500mm f4.5. It's in fantastic condition and has apparently been hardly used. I've been very happy with the shots I'm getting.

One thing is niggling me though -

When autofocusing for a subject such as a bird in flight, if i lose the subject against a relatively clean background, for example far off vegetation, the AF appears to hunt for a short time then gives up. I'm trying to work out if this is intentional so that it doesn't just constantly hunt, or if it's an issue with my unit. When it does this I then need to point it at something close, get it to start focussing again then try to re-obtain the subject. I also seem to sometimes have to manually remind it where to focus - once it's back on it's perfectly OK. I've tried it with the focus limiter in all positions and it still happens.

Any ideas?

Thanks in advance

TobyH

 

Keith Reeder

Watch the birdie...

• Jan 12, 2011

• #2

What camera?

And is it (the camera) set not to try to focus in those circumstances?

A few Canons have that specific option (custom function III-4 on my 7D for example - "Lens Drive When AF Impossible"), and others might too.

It sounds very much like this custom function.

 

a.dancy

Registered User

• Jan 13, 2011

• #3

Mine is the same and it needs to be repaired. Also very cold conditions makes it worse.

 

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TobyH

Well-known member

• Jan 13, 2011

• #4

Thanks for the responses. Totally forgot about camera info /slapmyself.

I'm using a Nikon D300. I hadn't thought about custom settings but will check.

a.dancy - you seem sure it needs repair - have you looked into this already?

Thanks

TobyH

 

a.dancy

Registered User

• Jan 13, 2011

• #5

Yep, response the same no matter what settings or camera.

 

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TobyH

Well-known member

• Jan 14, 2011

• #6

Thanks. It's not that much of a problem that I'll send it in for repair right now but i'll bear it in mind for whenever it does end up going in for repair maybe in the future.

 

Keith Reeder

Watch the birdie...

• Jan 14, 2011

• #7

So you've ruled out the in-camera settings then, Toby?

 

a.dancy

Registered User

• Jan 14, 2011

• #8

My god check your settings first Toby! Similar or same symptoms can have variable causes.

If you do send it in please get back and let us know what the problem was precisely...and of course the cost.

It's a great lens Toby so don't let the hiccup put you off enjoying it.

 

Keith Reeder

Watch the birdie...

• Jan 14, 2011

• #9

a.dancy said:

My god check your settings first Toby! Similar or same symptoms can have variable causes.

Click to expand...

I'll say!

I was all ready to bundle up my 7D today because all of the AF modes except the "basic" single AF Point mode had stopped working - All AF Points, Zone, Expanded - they were all dead, and I was 100% certain that nothing I'd done could have caused this across-the-board failure.

It looked and felt like a software issue: I'd done a hard reset (taking out all the batteries including the "clock" battery), and confirmed the behaviour by testing with other lenses, which were no different.

And I'm a committed RTFM guy.

Thing is... A few weeks ago I'd changed the button I use for back-button AF.

This shouldn't have made a blind bit of difference to whichever AF mode I was using except that I've got my most-used other AF modes saved to Custom User settings on the main dial: what I'd not realised was that the change I'd made to the back button in "normal" mode wouldn't carry across to the Custom User settings. It simply never occurred to me that this wouldn't be a universal change.

So turning the main dial to (say) C1 for Expanded AF mode automatically switched the back-button AF back onto the button I was using when I first saved the user settings..!

As I say, I was literally wrapping the camera in bubble wrap for its trip to the repairer when it suddenly occurred to me to check the effect of twisting the dial on the saved Custom User settings!

Too complicated by half, modern cameras!

 

Last edited: Jan 14, 2011

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TobyH

Well-known member

• Jan 15, 2011

• #10

I seem to have misunderstood that a bit

I thought a dancy was saying he'd fully checked it out when he had the issue and it hadn't helped. I will certainly check my settings (when I get my body back from getting a new shutter !!) I'll check the manual fully and hope I understand it

Thanks for the advice guys, i'll give it a thorough investigation once my D300 is back, sometime this week.

TobyH

 

Keith Reeder

Watch the birdie...

• Jan 15, 2011

• #11

I'm sure Adrian would have checked everything out, Toby - but that would definitely have included eliminating the camera as the source of the "problem".

So in his case checking out the camera didn't help - but you need to be sure that it's the same for you.

While you're without your D300, can you test the lens on a friend's camera?

 

Last edited: Jan 15, 2011

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TobyH

Well-known member

• Jan 15, 2011

• #12

Fraid not Keith, all the people I know around me have Canon bodies. Not long to wait though, should have it back midweek.

TobyH

 

a.dancy

Registered User

• Jan 15, 2011

• #13

Everything checked out! furthermore other long lenses perform on the camera in the manner I would expect them to.

 

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ilovesonatas

New member

• Jan 30, 2011

• #14

Hi TobyH

I'm new user from Hong Kong and I am recently using D700 & D300 with two Sigma lens, 150-500mm f5~6.3 APO DG OS HSM and 300mm f2.8 APO DG HSM. My experience is that, when you use AFC but using only the center point for focus, it do stop to focus if it can't find the subject. Even though I use Nikkor Mico 200mm AF-D lens, I point to the balloons in the sky and it can't auto focus until I change the subject (if the center point not against the balloon) to focus the clouds rim. It is better to choose the focus point to 51 points (better 51point -3D). I wish it can help.