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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Re: Auto-focus lens now only worka mNUlly
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!
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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 Sigmaphoto.com 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.
Usually the gears will strip the lens gears which tend to be plastics whereas Sony a cameras themselves have metal driven cogs....I once stripped a sigma zoom using an
A700 simply because the motor on that camera had no feedback on torque...put a different lens to check this out first...then check the faulty lens the cog is visible once you remove the rear mount.
I recommend that you print this test chart: http://www.photo.net/learn/focustest/scale45.jpg
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.
Then examine the picture in your computer, zoomed to 100%. Now it should be clear wheter you got back- or front focus, and how large the problem is.
Unfortunately, there is no way for you to adjust the camera and lens combination yourself, you will have to send/bring the camera to an autorized camera workshop. This is covered by the warranty.
Hope this helps!
Did it ever work on this camera?
I have seen some Sigma lenses that are auto focus on canon film cameras but then when put on the digital they dont work right. If you have used it on this camera then make sure the lens is clean.sometimes dirt on the front wil make it try focusing on the dirt. Next try focusing in manual focus to make sure the focus is working. Then take the lens off and then put it back on and make sure it clicks into place.
Let me know if none of those things work. also make sure to try focus on something close and somthing far away.
well after a week in the shop it came back working. the guy at the shop could only tell me that the repair people had fixed a problem in the auto focus (he had no other information). So the solution here is going to a place to repair your lens. if someone finds the cause of this problem it would be great
My first suggestion is to send it back if it is under warranty.
The grease probably got so thick, from the cold, that it caused too much resistance for the auto-focusing mechanism. You probably have damaged the focusing mechanism in the lens. You cannot repair this, yourself. I don't know how cold is too cold but it really shouldn't have done that.... Tamron makes cheap lenses. Try and exchange it for at least a Sigma.