Does all Sigma 120-300 OS lenses have this focus problem?

I bought a new Sigma 120-300 OS lens this week and went photographing some birds in flight. I made three trips this week with the lens and every time there were some haults with the lens af. Sometimes the lens didn't get focus on a bird and the motor just tried to do something.

I told my story on a small forum and I got several same kind of stories with their Sigma 120-300 OS lens. All of those lenses were with Nikon mount. ( actually I haven't talked anyone who doesn't have this problem and have tested this )

I found one clear way ( didn't try many different ways ) to repeat the problem over and over again.
1. focus quite close ( 3-5m )
2. then try to focus something above you further than 10m

-> AF-motor just halts and camera doesn't get any focus. Some times camera got the focus after 10s of trying.

I did a small video which shows the problem more clearly:
http://vimeo.com/30234259

Now I would be really intrested to hear does anyone else have noticed this problem? Can anyone repeat the problem with their own lens? Are all problematic lenses with Nikon mount?

If this is more a "feature" than a problem which can be fixed for good, I won't be looking after Sigma lenses anymore. It's really annoying when you get bird flying over you and the lens doesn't focus.

Yake that len's back to the store where you goti it. Looks like you "lost" at the Sigma lottery. (I myself will never buy a Sigma lens.)
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Ken
Sony Alpha Seventy Seven

harleydavidson said:

Yake that len's back to the store where you goti it. Looks like you "lost" at the Sigma lottery. (I myself will never buy a Sigma lens.)
--
Ken
Sony Alpha Seventy Seven

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Of course I will, but this looks like a wider problem than a Sigma lottery win. I have discussed with three other photographers who have this lens and everyone has had this same problem.

Unlike Canon Teles., that lens doesn't have a Focus Limiter.

Canon AF can/will falter if the Limiter is not set for the "correct" distance.

Not sure if that's your problem, but you might try turning the Focus manually to get close/er to the target distance prior to attempting AF. (Example: For BIF try manually focusing on a cloud near the height of the bird; or a tree,etc. that appears to be about the same distance as the bird.)

Leigh

http://www.leighwax.com

I just tried mine on my D80 and it works fine. No birds flying by, but if I focus on something within a few metres then focus on a distant tree branch, it snaps into focus quickly.

I don't have this problem with my non OS 120-300 but I have several Sigma lenses and I have had 2 of them that needed the auto focus mechanism repaired (300-800 and 50-150). Sigma repair service is quick and accurate. If you replace the Sigma lens, you may just get another bad one. If you get it fixed, it will operate perfectly when you get it back, at least mine did.

I have the non-OS version (the DG version) and I do not have this problem...if it is a problem. I think you are asking too much for this lens. Also, not sure I understand the issue - focusing on a close subject and then focusing on a distant subject?

You were moving the lens fairly quickly in the video, and I am not sure if you held the shutter release down continuously or simply pressed the shutter each time you "drew a bead" on a different focus point. Were you in continuous focus mode (C) or single servo mode (S)? Seems also that since you are focusing on trees with numerous leafs, was the focus point on a specific leaf?

Personally, I think this is a great lens for the price and I am very happy with mine. Sigma makes great lenses and to the poster's remark about the "Sigma Lottery," that is being perpetrated by a few dissatisfied customers who believe in perfect copies of lenses - there are none and all have their limitations, including the Nikkors. Keep in mind that Sigma makes a great many lenses for many different camera manufacturers (and sometimes the lens and camera don not "talk" to each other correctly), whereas Nikon only makes one. I have nothing against Nikon (I have four cameras and a few Nikon lenses), but I also use Sigma and Tamron lenses as well.

My suggestion, since it is under warranty, send it to Sigma for review.

Best wishes on the outcome.
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http://www.dusing.zenfolio.com/
DanD

Hi, been one or two complaints of this in the Canon forums.

Basically manually turn the focus to the closest setting and try then to focus up > 45 degrees to (in my case) a TV aerial.

Mine does the same but it struggles for 2 to 3 seconds and then finds focus. I notice your one is 'worse'.

I believe it also works the other was round .... set the focus manually to infinity and then point down at something close & it struggles here.

Mainly happens at 300mm.

I'm going to contact Sigma and see what they say.

Keep is informed as to how you get on.

Jim

I bought one of these lenses in Nikon mount in mid August and replaced it twice before giving up with Sigma at the end of October. The lens is outstanding optically but the focus is unreliable on static subjects and fails totally on even the slowest of targets moving towards the lens. I shot over 2000 images on two different cameras in those two months and overall only 50% of the images (mainly static subjects) were sharp. Its worth mentioning that all these images were taken using the centre focus point with the lens mounted on a sturdy tripod (with OS off)

I'm most disapointed and it would seem that I'm not alone in finding problems with this lens. My guess is that there's an interface problem between lens and camera as I noticed that even when the camera was set to release only on confirmation of focus in viewfinder it would often take images which when viewed in the software were clearly out of focus. To my eye it seemed as if there was a significant delay in the "mechanics following the electronics" as static subjects were comendably sharp but even slow moving ones were severly back focused.

Sigma UK have suggested that my expectations of the lens were too high I would suggest that a £2k lens should be able to focus on a duck swimming slowly towards it in bright sunlight and that rather than insulting the intelligence of their customers they might wish to sort the problem out.

Yes, I also have this problem. Bought a 120-300 OS (used) a couple of days ago and it exhibits the same problem as you are describing.

Looks like some of the responders in this thread did not fully understand what's going on here. This is not a simple hunting/focus limiter problem. This is something mechanical, like a slipping clutch or coupling issue.

Mine does this when the FL is above 250mm and the lens is pointed upward. The AF is unable to rotate to the distant AF settings. But this happens in manual too. Tried turning the AF ring to achieve focus when tilted up and it sort of gets stuck in the middle and slipping. Ring turns but does not turn the internal focus mechanism.

But just like the OP mentioned and demonstrated, if you pre-focus something far at a horizontal position, then tilt up, it will achieve focus in the vertical position too. So basically, there is some problem in the middle of the AF range which prevents is going from close focus to distant focus in a vertical or near vertical position.

Others in this forum have had the same problem too. But I know at least one person whose lens was repaired by Sigma and it works properly now.

Other thread for this issue:

http://forums.dpreview.com/forums/readflat.asp?forum=1029&message=39497952&q=sigma+120300+coupling&qf=m

Sorry to ressurect this but its worth it i think. Having the same issues with my 120-300 OS. Sent already twice to Sigma Germany for service but those service sessions have not fixed it. On static subjects the focus rate although not as it should be is marginally acceptable , but if the target slightly moves especially inbound or outbound you get most of the time an approximate focus (severe back or focus focus) My previous than this gen 120-400 (bought used) nails focus at all circumstances, even in low light situations, while the 2k 120-300 is expected to perform even better than the 120-400, instead has been kept since purchase in its case due to complete lack or reliability

I've had mine about 2 months now.. once in a while it gets hung up at infinite for a second.. it makes a faint whine.. i can never get it to repeat.. i'd say maybe 6 times since I've had it.. Other than that its been awesome...
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My sober voyage into bird photography

If I move from one extreme to another, there is a slight delay in auto focus. It only seems reasonable to me that if you are focusing at a short distance then go to infinity or vice versa, it takes the lens longer to adjust than if you cover a shorter span.

Kris in CT said:

I've had mine about 2 months now.. once in a while it gets hung up at infinite for a second.. it makes a faint whine.. i can never get it to repeat.. i'd say maybe 6 times since I've had it.. Other than that its been awesome...
--
My sober voyage into bird photography
http://www.facebook.com/KristoferRowePhotography

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Thanks for the encouragement.