I have a Canon Rebel XTi and a Sigma 70-300mm f/4.5-5.6 and my auto focus system is being very spastic. Not wanting to focus. What should i do?
Your camera has 3 focus modes M manual, C continuous and S single. Set it to S and that should solve the problem but when you change focus points you will have to push shutter button halfway again, you also might not have enough light for your camera to see try it on a brighter subject to find out
You have to replace the very glazed disc rotor or have it resurfaced, yes you can try to sand it but it is very hard metal. But this is causing the noise.
lube the moving parts and back of pads with copper grease
You're probably trying to focus on something without much definition. (Like a White background). If this is the case. Turn off your auto-focus and focus manually. ___ Take the lense off the camera and inspect the terminals on both the camera and the lense. Make sure theres no dust or anything in between. And when you put the lense back on, make sure it snaps tight and made proper contact. Also, try another lense and make sure its not a problem with the camera. If these don't work, definetly send it back.
Either not enough light to focus, not enough contrast for your autofocus to work or you've got a problem with your lens. Try turning the autofocus assist light or finding more contrast against your subject. If that fails you'll need to turn off the auto focus and do it manually. If that doesn't work, replace the Sigma with something made by Canon.
