My autofocus on my canon 500d camera is not working properly. I find i have to switch to manual focus to take the pictures, even in all the atoumatic settings. I have only noticed this problem occurring in the past few weeks. When I try and take a photo, I press the shutter half way down to focus and the camera just flashes continuously until i remove my finger. It also fails to focus. PLease Help :) Melanie

With sand in the lens it plays havec because it hinders the performance and the proper functionality of the lens. I strongly suggest having it checked by a professional.

Your 100mm lens autofocus not working.it may be due to autofocus flex cable inside the lens damaged. It is replaceable part. You may have to contact service technician. However when you switch to manual mode it should focus & click. Try it.

If it is a dark scene and the camera cannot detected edges well the autofocus will either move around a lot or simply will not focus and thus wont expose. You will just have to manually focus or use the flash

Is this happening when you try to focus on something pretty close to the camera?
If that's the problem, it's because the lens has a focus distance 0.25m/0.8ft meaning the subject has to be this far away for the lens to be able to focus. You could buy a new lens with smaller focus distance if this is a big problem to you.

To autofocus the sensor needs a fair amount of contrast (light and dark eges) to operate. If you're trying to take a photo in a dim room of a dark colored subject for instance the focus won't lock and the camera won't take the picture. Try switching your lens to manual focus and shoot that way.

Even if you are a millimeter closer than the lens is able to focus properly, the shutter will not fire....back up a little.

Does your lens try to focus or it doesn't try at all? You will have to understand that for the camera to autofocus successfully, theere should be adequate light and contrast. That means, autofocus often fail to focus even colored walls or objects under dim light. If you tried all this in daylight, outdoors, then the autofocus sensor is faulty. Please reply with details of how you tried the af.

ho.....ho...
I have this prob in my canon EOS kiss SLR.
CHECK THAT>>>>>>>
Hold the camera vertically.Switch on the AF and let the camera to auto focus.!!!!!!!!!!!!!!!!
Don't wondering....Check ur camera's sub mirror in the in side of the sub mirror.The spring that push back sub mirror from the main mirror is broken.......!
How to repair this? Follow this link....
http://www.facebook.com/home.php?#/album.php?aid=2042115&id=1359757176
bye..

Hello,
It's possible that the reason the "pictures turn out fairly good" is that your f-stop is set high enough that even though the image isn't properly focused, you have enough depth-of-field to bring your subject into "near focus". Does your lens try to focus back and forth when you half-press the shutter? If not, double check that the lens is in autofocus and not manual focus. You can also try cleaning the contacts between the lens and camera. Take the lens off, and then one-at-a-time clean the contacts on both the lens and the camera, using a clean pencil eraser. Gently rub the contacts. Be sure to hold the item upside down so that the eraser debris falls on to the table, not into the camera body or lens!

If none of this helps the autofocus may have become damaged and you need to have the lens and camera looked at by Canon Repair.

I dropped my camera and thought the autofocus broke. It turn out that it swithed from autofocus to manual focus. There's a switch on the lens. Check if that's your problem too.