Autofocus issue with Sigma 10-20mm? Help!

Started 9 months ago | Discussions
banflu
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Autofocus issue with Sigma 10-20mm? Help!
9 months ago

Hi everyone,

Been lurking for a while but finally registered here as I ran into a problem!

I bought a Nikon D5100 a few months ago (my first DSLR) and after a while I noticed that I really started to like wide angle photos so I also bought a Sigma 10-20mm f3.5 lens. From the start I had a feeling that it's autofocus wasn't 100%, but at first I thought nothing of it - I am only a beginner after all.

But recently I was on holiday so I used the camera (and this Sigma lens) quite a lot .. and I've had quite a number of out-of-focus photos. I later realised that they are never out-of-focus if I use live view. Of course, live view is much slower so it is quite an issue.

Anyway, after making extensive testing I came to the conclusion that the Sigma lens is to blame. Please take a look at this video: http://www.youtube.com/watch?v=zOeoLUQrp_A

In this test I placed the camera on a small tripod (gorilla pod) and attached a focus test chart on the wall. I focused on the chart multiple times using live view. It always focussed perfectly - any photo i take in live view is 100% in focus. Later I put it out of live view, and the focus setting is visibly different in the focus window on the lens. Also, the focussing is inconsistent when not in live view. Put it back to live view and it becomes 100% consistent and perfect.

I later tried this same test with a Nikkor prime 50mm lens, and it worked perfect - the focus is always exactly the same, both in live view and in normal view.

Any thoughts? Has anyone else had a similar issue? The lens is still under warranty ... should I try to get a replacement, or should I fork out more $$$ and get a Nikkor 10-24mm?

Many thanks in advance for your help!

Nikon D5100 Sigma 10-20mm F3.5 EX DC HSM
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mosswings
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Re: Autofocus issue with Sigma 10-20mm? Help!
In reply to banflu, 9 months ago

banflu wrote:

Hi everyone,

Been lurking for a while but finally registered here as I ran into a problem!

I bought a Nikon D5100 a few months ago (my first DSLR) and after a while I noticed that I really started to like wide angle photos so I also bought a Sigma 10-20mm f3.5 lens. From the start I had a feeling that it's autofocus wasn't 100%, but at first I thought nothing of it - I am only a beginner after all.

But recently I was on holiday so I used the camera (and this Sigma lens) quite a lot .. and I've had quite a number of out-of-focus photos. I later realised that they are never out-of-focus if I use live view. Of course, live view is much slower so it is quite an issue.

Anyway, after making extensive testing I came to the conclusion that the Sigma lens is to blame. Please take a look at this video: http://www.youtube.com/watch?v=zOeoLUQrp_A

In this test I placed the camera on a small tripod (gorilla pod) and attached a focus test chart on the wall. I focused on the chart multiple times using live view. It always focussed perfectly - any photo i take in live view is 100% in focus. Later I put it out of live view, and the focus setting is visibly different in the focus window on the lens. Also, the focussing is inconsistent when not in live view. Put it back to live view and it becomes 100% consistent and perfect.

I later tried this same test with a Nikkor prime 50mm lens, and it worked perfect - the focus is always exactly the same, both in live view and in normal view.

Any thoughts? Has anyone else had a similar issue? The lens is still under warranty ... should I try to get a replacement, or should I fork out more $$$ and get a Nikkor 10-24mm?

Many thanks in advance for your help!

Talk to Sigma about your focusing issues. Provide them with sample pictures demonstrating the problem. It is possible that your lens is out of calibration, in which case Sigma should accept it for warranty service. The focusing inconsistency, though, is another issue. I have the older version of the 10-20, the f4-5.6, and it shows no such inconsistency in focusing. Usually, UWA lenses have relatively few focusing issues because of their extreme depth of field and relatively slow maximum aperture. There is a natural spread to PDAF focusing results, but usually the spread is very tight. Double check as well that you are not at or near the minimum focusing distance of your lens. It varies with FL.

The Nikon 10-24 is a fine lens, but more expensive than the 10-20. It might work better than the Sigma does, but there's no reason why your 10-20 should perform as it does.

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jkjond
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Re: Autofocus issue with Sigma 10-20mm? Help!
In reply to banflu, 9 months ago

banflu wrote:

Hi everyone,

Been lurking for a while but finally registered here as I ran into a problem!

I bought a Nikon D5100 a few months ago (my first DSLR) and after a while I noticed that I really started to like wide angle photos so I also bought a Sigma 10-20mm f3.5 lens. From the start I had a feeling that it's autofocus wasn't 100%, but at first I thought nothing of it - I am only a beginner after all.

But recently I was on holiday so I used the camera (and this Sigma lens) quite a lot .. and I've had quite a number of out-of-focus photos. I later realised that they are never out-of-focus if I use live view. Of course, live view is much slower so it is quite an issue.

Anyway, after making extensive testing I came to the conclusion that the Sigma lens is to blame. Please take a look at this video: http://www.youtube.com/watch?v=zOeoLUQrp_A

In this test I placed the camera on a small tripod (gorilla pod) and attached a focus test chart on the wall. I focused on the chart multiple times using live view. It always focussed perfectly - any photo i take in live view is 100% in focus. Later I put it out of live view, and the focus setting is visibly different in the focus window on the lens. Also, the focussing is inconsistent when not in live view. Put it back to live view and it becomes 100% consistent and perfect.

I later tried this same test with a Nikkor prime 50mm lens, and it worked perfect - the focus is always exactly the same, both in live view and in normal view.

Any thoughts? Has anyone else had a similar issue? The lens is still under warranty ... should I try to get a replacement, or should I fork out more $$$ and get a Nikkor 10-24mm?

Many thanks in advance for your help!

Interesting to see your video. I'm not sure what I can learn from it as there's no support information. One important aspect is where the focus point is set, or are you using a pattern array for the camera to decide? Posting sample images may have been helpful.

I have a 10-20 and found it very sharp, and as your 50mm is performing fine I'd suspect you have a duff copy of the siggy. With WA the DOF is usually large especially on DX, so focus issues are rarely a problem. Lenses and bodies have an accepted tolerance when it comes to focus - your body may be at one extreme and the WA at the other, yet your prime could well be just as far out as your WA but a better match for your body.

I'd look into the warranty.

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Wedding and fine art photographer based in the Lake District, UK

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Ronan_M
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Re: Autofocus issue with Sigma 10-20mm? Help!
In reply to jkjond, 9 months ago

that focus chart seems to be awfully close to the camera. What's the minimum focusing distance for that lens?

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banflu
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Re: Autofocus issue with Sigma 10-20mm? Help!
In reply to Ronan_M, 9 months ago

Thanks all for the replies.

The focus chart was 1.5ft away (according to the focus ring). Minimum focus distance is less than 1 ft. about 24cm.

In response to jkjond, I was using the centre focus point, and it was looking directly at the centre of the focus chart. So, in my opinion the focussing should have been very consistent (as was the case with the 50mm prime).

I will go to the shop on Saturday hopefully and see what they think.

Cheers

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Nexu1
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Re: Autofocus issue with Sigma 10-20mm? Help!
In reply to banflu, 9 months ago

Ironically, I noticed not too long ago that my wide angle Tokina 12-28 focuses more perfectly with PDAF.  I wonder if any of this is related to 3rd party lenses just not always meshing perfectly with the body.  FWIW my tokina doesn't get to infinity focus fast enough in CDAF.

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Jimmy C
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Re: Autofocus issue with Sigma 10-20mm? Help!
In reply to banflu, 9 months ago

If your good in LV and not good through the view finder, is it possible you are using two different sensors in the test.  I have the D7100 and there is a different sensor used for LV.  The Nikon lens will have the correcting data in the camera so you may not notice similar issues with the 50mm.   I'm not familiar with the 5100, but can you do a fine tuning of the WA lens?

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mosswings
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Re: Autofocus issue with Sigma 10-20mm? Help!
In reply to Jimmy C, 9 months ago

Jimmy C wrote:

If your good in LV and not good through the view finder, is it possible you are using two different sensors in the test. I have the D7100 and there is a different sensor used for LV. The Nikon lens will have the correcting data in the camera so you may not notice similar issues with the 50mm. I'm not familiar with the 5100, but can you do a fine tuning of the WA lens?

You are always using a different sensor with Viewfinder AF. Viewfinder AF uses a separate sensor at the bottom of the mirror chamber, but LiveView uses the image captured by the main sensor itself. The LiveView image is always the more accurate, inherently. Unfortunately, only D7000/D7100 and higher end Nikon bodies have AF Fine Tuning.

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Leonard Shepherd
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Re: I have come to a different initial conclusion
In reply to banflu, 9 months ago

banflu wrote:

recently I was on holiday so I used the camera (and this Sigma lens) quite a lot .. and I've had quite a number of out-of-focus photos. I later realised that they are never out-of-focus if I use live view. Of course, live view is much slower so it is quite an issue.

If you bought a similar Nikon lens instead the Nikon lens instructions would caution ordinary AF is not always accurate with the fine detail or small subjects under the AF rectangle. This can be common with wide angle lenses.

As you have not posted any images it is likely you have problems with subjects that are poor for ordinary AF, and the photos that are sharp are better AF targets. Small example images could help clarify if this is your problem.

Nikon suggest when AF is not good find an alternative subject at the same distance (not always possible) or use manual focus.

LiveView as you noter is much slower to use but as it detects a very small segment of the subject it can sometimes beat ordinary AF with static subjects.

LiveView is not much use with moving subjects, and also needs detail in a horizontal direction to ensure it works accurate.

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If they are great images does what lens, body or technique was used matter more than the skill of the photographer?

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banflu
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Re: I have come to a different initial conclusion
In reply to Leonard Shepherd, 9 months ago

Live View @ 10mm, f3.5, 1/15sec, ISO 1250

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banflu
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Re: I have come to a different initial conclusion
In reply to Leonard Shepherd, 9 months ago

NOT Live View f3.5, 1/25sec, ISO 1250, Focal length 10mm   (on a tripod)

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banflu
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Re: I have come to a different initial conclusion
In reply to Leonard Shepherd, 9 months ago

As you can see I have just posted two sample images, taken from the same place on a tripod.

In both cases I focussed on the same place - on the top left muffin

The non-live view picture shows serious back focussing. And at first I thought this was the problem. But after more testing (as per video) it seems that it does have a back-focussing problem, but it varies - it is inconsistent.

This is another example - all subjects are on the same plane with good contrast and good enough lighting - this picture should not be out of focus!

If you wish i can send the raw pictures by email .. or let me know where I can upload them.

thanks once again

Not live view  - 10mm @ f3.5, 1/30sec, ISO 1250

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banflu
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Re: I have come to a different initial conclusion
In reply to banflu, 9 months ago

So I went to the shop today where I bought it from.

He assured me that these are very good lenses and that they have not had one return of the 10-20 lenses, even though they are selling well (so he said).

Anyway, I showed him the problem: I placed a brochure i found in his shop about 40cm away, focussed and took a picture using live view. Then without moving the camera I went out of live view and focussed again. The focus ring immediately moved every time I half-pressed the shutter button. I took 2 pictures - both came out-of-focus.

He suggested to test a new lens because he had one just like it in stock in the shop. We tried it and guess what - it performed exactly the same as mine. So he wouldn't accept that mine is faulty as the new one performed exactly the same (and the serial numbers weren't close).

He then suggested to take it to their main shop, where he said that someone would be able to calibrate it using a USB dock. I checked about this but I found out that the USB Dock is not compatible with the 10-20mm lens.

Any suggestions?

From my side, as I told the salesman... if we conclude that all Sigma 10-20mm f3.5 lenses are like this, I am definitely NOT happy with it. It makes me sad really because I love it's photos when taken in live view!

Oh and one last thing. I tried both 10-20mm lenses on another body (a new D5300) but autofocus did NOT work in live view. So we couldn't make conclusive tests on it. After a quick web search it appears that there are in fact autofocus issues with the D5300. Shame.

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banflu
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Re: I have come to a different initial conclusion
In reply to banflu, 9 months ago

These are the pictures I mentioned in the previous post.

Both shot @ 12mm, f3.5, ISO 320, 1/40 sec

Focus mode = single servo, single point (centre)

live view

not live view


not live view

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