question to Sigma 8-16mm users

Started Aug 14, 2011 | Discussions
ManuH
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question to Sigma 8-16mm users
Aug 14, 2011

I just got my Sigma 8-16mm and my copy seems good optically however the AF hunts like crazy on my K-5 (and the same on a K10D). It will go back and forth and sometimes will find focus sometimes not. Liveview AF is a little better but still not perfect. And the problem seems even more sensible at close focus.

Is it something experienced by other 8-16 users or I will have to return or to send it for fixing?

Bich
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Re: question to Sigma 8-16mm users
In reply to ManuH, Aug 14, 2011

same problem for me.
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PG Thomas
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Re: question to Sigma 8-16mm users
In reply to Bich, Aug 14, 2011

Have you tried reducing the number of focus points to 5 - or just using spot focus?

Methinks that the hyperfocal distance of this lens must be practicaly 1m to Infinity! So I guess any AF system would have problems.

Clearly the K5 doesn't 'know' this lens. I wonder if, in future, this could be possible feature of the Menu, As I guess critical focus is somewhat irrelevent.

Pete

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Philnw2
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Re: question to Sigma 8-16mm users
In reply to PG Thomas, Aug 14, 2011

The 10-20 had AF problems at 10mm but these went away at 12mm and up.

I always thought it had to do with the focus areas being so close together, that focus was pretty much irrelevant at lower FL. I used to just set the manual focus ring at just below 3' and it worked well at that setting for DOF to infinity.

I suspect you will find something similar for the 8-16
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miles green
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Re: question to Sigma 8-16mm users
In reply to ManuH, Aug 14, 2011

No problems here.

I always choose my focus point manually and use the back button AF, with no AFing on the shutter release. Actually, I think it's fast and stealthy, but it's my only HSM lens.

I would make sense if the AF system get confused on what to focus on, given all the things that you can fit in the frame at 8mm!

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Miles Green
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Ishpuini
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Re: question to Sigma 8-16mm users
In reply to miles green, Aug 14, 2011

miles green wrote:

No problems here.

I always choose my focus point manually and use the back button AF, with no AFing on the shutter release. Actually, I think it's fast and stealthy, but it's my only HSM lens.

I would make sense if the AF system get confused on what to focus on, given all the things that you can fit in the frame at 8mm!

Same here. No problems, and I work the same way.

Wim

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ManuH
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Re: question to Sigma 8-16mm users
In reply to miles green, Aug 14, 2011

miles green wrote:

I would make sense if the AF system get confused on what to focus on, given all the things that you can fit in the frame at 8mm!

Maybe for relatively distant subject. But when I try to get closer in the below 1m range, most of the time it just give up. I have used the Sigma 10-20mm, Pentax 12-24mm, DA 15mm and DA 10-17mm and never ever experienced something like that on an ultrawide. Even when set at 16mm my Sigma 8-16mm is still hunting.

This is very important to know if this behaviour is on all the 8-16 or just mine. So I know if it has to be fixed or returned (and mourn by just sold 12-24).

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Twong
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Re: question to Sigma 8-16mm users
In reply to ManuH, Aug 14, 2011

I have the 8-16 for almost a month and never experienced any problem close up or distant objects on my K5 or Kx. I also have a Sigma 10-20 and no problem either.

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miles green
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Re: question to Sigma 8-16mm users
In reply to ManuH, Aug 14, 2011

I fear it's just yours. Sorry.
Mine works like a charm, a true architectural workhorse, fast and razor sharp.

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Miles Green
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Kyogle
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Fine on my K10D
In reply to miles green, Aug 14, 2011

Focuses more or less instantly on distances closer than 1 meter. Fine for all other distances too.
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Gerry Winterbourne
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Re: question to Sigma 8-16mm users
In reply to ManuH, Aug 14, 2011

Two things that other people have mentioned can work together for you: even at its longest FL of 16mm its hyperfocal distance at f/6.7 is only 6ft (2m) so everything from 3ft (1m) to infinity should be in focus if you set your range to 6ft (and all the distances are halved when you go out to 8mm). However, this isn't that easy do so what I do is use single focus point and select the one below centre in whichever orirntaion I hold the camera.

This means you don't focus at the exact hyperfocal distance but you do pick something in the reasonably near foreground. With just the one, reasonably close area that is big enough to show reasonable contrast, focus is near enough instant.

Try doing the same with yours: if it is still slow to focus the lens is faulty.

Photozone hasn't tested this lens on Pentax but f/6.7 is the single aperture that seems to give the best compromise between centre and edge resolution at all focal lengths when tested on Canon.

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fotobert
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mine too
In reply to ManuH, Aug 14, 2011

...but I don't worry about this. When stopped down to f9 you don't have to focus at all

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ManuH
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Re: mine too
In reply to fotobert, Aug 15, 2011

fotobert wrote:

...but I don't worry about this. When stopped down to f9 you don't have to focus at all

That's OK for distant subjects but for close subjects, I cannot accept that. No other lens does this, even my DA 10-17 which also has a huge DOF. I'm going to test another 8-16 if I can.

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ManuH
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UPDATE: It's fixed
In reply to ManuH, Feb 21, 2012

ManuH wrote:

I just got my Sigma 8-16mm and my copy seems good optically however the AF hunts like crazy on my K-5 (and the same on a K10D). It will go back and forth and sometimes will find focus sometimes not. Liveview AF is a little better but still not perfect. And the problem seems even more sensible at close focus.

Is it something experienced by other 8-16 users or I will have to return or to send it for fixing?

An update for those who have the same problem: it's fixed.

I had to send it to Gentec (repairs Sigma in Canada) two times. The first time they returned me the lens pretending it was fixed but it was worse: it was electronically dead (No communication at all with the camera). The second time they did it right and now the lens doesn't not hunt anymore and is quite fast to reach focus. Although sometimes it gets past infinity but I guess it's normal for such an ultrawide.

The repair time was about 6 weeks in each case. Which means I couldn't use this lens for a few months. I'm not that impressed with Sigma/Gentec. Pentax has been much faster for me.

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MightyMike
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Re: UPDATE: It's fixed
In reply to ManuH, Feb 21, 2012

I guess its different when you live just 40 minutes away from Gentec and you get to know the guys working there... 6 week turn around time with shipping ain't that bad, i've heard of people complain about 3 month turn around times at Pentax Canada. for me i just drive the lens over and sometimes have them ship it back, sometimes i pick it up myself. But then that would be a long haul for you. Sometimes the service people miss the problem but then that happens with every service company.
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t3hh
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Re: UPDATE: It's fixed
In reply to ManuH, Feb 24, 2012

The repair time was about 6 weeks in each case. Which means I couldn't use this lens for a few months. I'm not that impressed with Sigma/Gentec. Pentax has been much faster for me.

I wish I could say that it's the prize you have to pay for using Sigma. But then I remembered how I had to return my FA 31mmLt after six months of using. I guess these are the times we are living in when it doesn't really matter how expensive/cheap equipment you buy - you never can be sure about the quality. BTW I also happen to own Sigma 8-16 and I love it!

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