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09-15-2013, 02:27 AM   #1
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K-5 and Sigma 70-200 2.8 HSM OS APO problems

Hi guys!
I've finally gotten to the point that I'm desperate enough to hassle you with a problem I'm facing for a six months now.
The combination of camera and lens that I have doesn't auto focus reliably. I've calibrated the set multiple times, even had it cleaned, checked and re-calibrated by a professional.
The lens has been re-flashed by Sigma (NL) but still...
I've tried every tip I could find on the internet but I'm not happy with the number of sharp images.
Even at center point fixed AF it manages to focus behind the (static) subject.
I've assembled two sequential images with exif data, does anybody have an idea what the ??? is causing this?
Thanks a lot for any useful response! :-)

What happens is that AF and AE are completely mad and remain like this for a few frames, frame rate sometimes doubles (as when AF-S is used).
The AF in the first image is behind but okay, these dogs are approaching at about 50km/h so that's probably explainable
(however I'm dissapointed by this phenomenon, I usually "fix" this by adding 10 steps to the corrected AF Fine adjustment)


09-15-2013, 02:34 AM   #2
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There must be something wrong with the lens contacts or electronics. Notice that in the second shot, there is no focal length or lens info.

Adam
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09-15-2013, 02:54 AM   #3
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Hi Adam, thank you for noticing and replying. I can even confirm this with another weird thing. Sometimes I get "MF" in the bottom of the display and the there's no focussing done at all.
The connectors should be clean, I've had the whole set professionaly cleaned a week ago and it hasn't been apart, it would be strange if the connectors have gotten this dirty I think?
09-15-2013, 03:13 AM   #4
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Something is terribly wrong yeah, it's like the camera loses contact with the lens. Dunno of the lens or the camera is at fault?

09-15-2013, 03:18 AM   #5
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That is a heavy lens, maybe the camera's bayonet is pulling away from the camera? Are the screws all done up tight? No other ideas, sorry.
09-15-2013, 03:23 AM   #6
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I've had similar issues with an older Sigma 105 macro. Sometimes the camera will start believing the lens is a manual lens - manual exposure, manual focus etc. It's been reported here a few times with several varieties of Sigma lenses.

In my case the result has often been hugely underexposed pictures. I believe it may have something to do with the alignment of the pins on the lens, or the quality of the pin's contact with the body. When I mount the lens, I am very careful to ensure it is turned all the way and everything clicks into place. I've also cleaned the body and lens contacts very carefully, and the problem seems less frequent after doing so. FWIW, I have several Sigma lenses - this is the only one that has ever had the issue.
09-15-2013, 03:25 AM   #7
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Thanks for your feedback guys!
There is indeed a small amount of movement between camera and lens but that is normal/acceptable on this type/size of lens according to my Sigma dealer, I've had them look at this right when I bought it.
(Canon L has this movement also for instance?)
09-15-2013, 03:34 AM   #8
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Tried my biggest Sigma, which is only a 17-70, but there is zero movement. If I had bent it any harder, I think I would have broken it.

edit: You need to try the lens on another camera, otherwise there's no way of knowing if it's the camera or the lens.


Last edited by calsan; 09-15-2013 at 03:41 AM.
09-15-2013, 03:40 AM   #9
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QuoteOriginally posted by rawr Quote
I've had similar issues with an older Sigma 105 macro. Sometimes the camera will start believing the lens is a manual lens - manual exposure, manual focus etc. It's been reported here a few times with several varieties of Sigma lenses.

In my case the result has often been hugely underexposed pictures. I believe it may have something to do with the alignment of the pins on the lens, or the quality of the pin's contact with the body. When I mount the lens, I am very careful to ensure it is turned all the way and everything clicks into place. I've also cleaned the body and lens contacts very carefully, and the problem seems less frequent after doing so. FWIW, I have several Sigma lenses - this is the only one that has ever had the issue.
Same problem with the same lens for me, I solved it by unscrewing the mount a bit and re-tightened it. Though yesterday I got some over exposed flash shots again and realized that the problem is back.
09-15-2013, 04:05 AM   #10
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:-)
I have the 17-70 also but this is waaaaaaay smaller than the 70-200. However, tightening the screws of the plate of the camera and lens "seems" to have reduced the margin.
Hopefully it was something "simple" as this, thanks a lot for the fresh ideas! ... Going to flash 1.15 now!
09-15-2013, 05:26 AM   #11
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I have non OS version of the Sigma 70-200 HSM II Macro on a K-7 and sometimes experience focusing issues like this. Particularly with moving subjects against a static pbackground. Originally had major problems and eventually dealer replaced it with a new one. This type of problem I put down to the lens picking up the stationary part of the background rather than what I hoped or assumed would be the focus point. When the subject fills more of the frame, focus seems to be better. I have a feeling the spot focus area is actually quite larger than indicated by the ( ) in the viewfinder. Something to experiment with.

Also on another Sigma, 105mm Macro with aperture ring I find sometimes the ring needs a little tweak to seat properly. Similar to what rawr describes.
09-15-2013, 06:25 AM   #12
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Interesting stuff... sounds like a reason to try and get the lens replaced. Too bad you don't have a second body so you could see if the same problem occurs with another K-5 or just yours. I'm guessing it's possible that if the electrical connections on both camera and lens are at the low ends of spec, it could cause an intermittent problem, where no electrical connection is made no matter what you do, and both companies could argue their product is with the specifications. Hopefully, it will turn out to be something you can nail down.
09-15-2013, 06:46 AM   #13
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I'm considering a swap also, the 17-70 hasn't done this (until now, I don't use this one so much).
Anyway, the 70-200 is going to Sigma Benelux tomorrow, let's see what happens...
09-16-2013, 12:42 AM   #14
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I just called Sigma, I got this explanation:
Beyond 120mm (depending on camera and light conditions) the AF-C doesn't keep up it it's normal for the system to become confused. (???)

edit: Lens is dropped off af Sigma, I can pick it up later this week :-)

Last edited by wpompen; 09-16-2013 at 02:03 AM.
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