Question about Sigma 28-70mm f/2.8-4.0 DG for Sony A100K, A100

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Auto-focus lens now only worka mNUlly

With Sigma 70-300 on Alpha-100, when the camera is turned on or off the lens makes a rapid clicking noise for about 5 seconds then silence. If the camera was turned on in an auto-focus mode after the noise it indicated it is in manual focus mode. The lens can be focused manually but does not go smoothly through the close-infinity range.

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  • tewargin Jun 25, 2009

    Camera off, set to manual focus.

    Mount lens.

    Turn on camera.

    Noise for 5 seconds.

    Lens works in manual mode.

    Set camera to auto focus

    LCD still says manual focus and lens still works manually.

    Set camer back to MF

    Turn off camera may or may not get noise.

    If lens not at infinity and camera turned on - lens goes to infinity then makes noise.



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This is not going to get into manual, provide in it is check its angle line to see some if you use the lens connected correctly to your camera. this is happen when you are not inserted it properly. this time call an assistance to guide and fix your lens. this problem now does not belong to the manual. Its an accident that lens are defective or factory defect. Hope might this well help you. Good luck!

Posted on Jun 26, 2009

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Put your camera / lens is in MF mode then check if the issue persists...

Posted on Jun 25, 2009


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How new is the lens? In or out of warranty? If out or warranty most likely solution is to find a Sigma authorized repair shop because your description sounds like the auto-focus motor gear has failed. If in warranty, check out for repair sites and also download the SIGMA_SERVICE_REQUEST.PDF. I've only had to deal with Sigma once on warranty matter and they were very helpful, provided UPS authorization for shipping on their nickel.

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Hello Abdul!
I recommend that you print this test chart:
Just print it on an ordinary paper, then put it on a table, and take a picture at it from a 45 degree angle, using the center focusing point only, aimed at the thicker line in the middle. The numers are centimeters. Take the test picture at f/1.4. Make sure you have good light so you get a fast shutter time. If you have a tripod, mount the camera on the tripod prior to taking the test picture.
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Did it ever work on this camera?
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Let me know if none of those things work. also make sure to try focus on something close and somthing far away.

let me know how it works,

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My first suggestion is to send it back if it is under warranty.

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Zoom lens

What camera are you using is the lens making a noise when it stops focusing  call sigma imaging uk 01707 329999

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