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06-19-2015, 07:53 AM   #1
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K-S2 focus oscillation with Live view

Have found this one problem with ONE of my lens. The Sigma 70-200M f2.8 HSM II, works with AF.S and AF.C. However using live view when I press the shutter button the focus never locks but oscillates backward and forward, from one end to the other. It does stop some times but at the nearest focus point. All the green focus points illuminate at the same time.

Edit. On further testing the oscillation goes from one end to the other twice and then stops. The number of green focus points depends upon the picture in view. Not supprisingly It also happens in movie mode, the AF oscillates when trying to get into focus before put into REC. Tried with my only other HSM lens 18-125mm no problems.


Last edited by fb_penpho; 06-20-2015 at 05:25 AM. Reason: Further investigation
06-19-2015, 12:00 PM   #2
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I think this could be related to lens firmware. I would contact Sigma to see if there are any updates available for the lens.

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06-20-2015, 03:19 AM   #3
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Is there a processing limitation?

In seeking to understand what is going on, I rechecked that I had not missed something with a screwdrive lens. I noticed that the lens refocused much slower (the drive speed had been reduced) under live view and movie then with AF.S and AF.C. The speed of the Sigma HSM was the same all the time. That is the camera had not, or not been able to reduce the speed of the HSM drive. So is it possible, that the problem is caused by a possible processing limitation under live view that means the focusing speed needs to be reduced?
06-20-2015, 06:20 AM - 1 Like   #4
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There are numerous threads here and on other sites about the Sigma 70-200 HSM II not focusing in CDAF (LiveView) on a number of bodies. It requires an update to the lens firmware.

06-20-2015, 06:53 AM   #5
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QuoteOriginally posted by THoog Quote
There are numerous threads here and on other sites about the Sigma 70-200 HSM II not focusing in CDAF (LiveView) on a number of bodies. It requires an update to the lens firmware.
Thanks for info, might just live with it using normal AF.
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