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04-07-2013, 06:44 AM   #1
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K5+Sigma 500mm autofocus freezes + F number not displayed

I have hard to pin down problem as it only happens now and again, so hard to know if its the body, the lens or the combination. What happens is the F number display on top plate goes to -- and autofocus freezes. After a couple of minutes it returns to normal. Seems like focus info not reaching camera? I have tried fiddling with switches and so on but cannot reproduce fault to order (or at all while I write this although it happened nicely as an egret landed near me this am :-(
I'm using AF continuous mode, spot AF. Auto exposure mode speed/F stop both fixed - variable ISO.

04-07-2013, 06:50 AM   #2
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Which sigma lens is this? Have you tried cleaning the contacts on the lens and camera?
The camera is thinking its in manual mode.
04-07-2013, 08:12 AM   #3
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Tighten the screws on the lens mount.
04-09-2013, 09:40 AM   #4
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have cleaned and will check screws, thanks both.

04-12-2013, 01:36 PM   #5
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I'm having intermittent balky AF issues (but no aperture data issues) with two of my Sigma zooms (100-300/4 & 70-200/2.8 HSM II) myself. It's driving me nutz! Strangely, they work fine when used with a TC. Checking the mount screws is a good suggestion.

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