Check the focus mode switch on the lens Autofocus will not operate if the focus mode switch on the lens is set to . Set the focus mode switch on the lens to , as shown in the image below.
 Clean the lens and camera electrical contacts The transfer of information between the camera and the lens is carried out by the electrical contacts on the camera and the lens.
 If the contacts on either the lens side or the camera side get dirty, communication cannot be carried out correctly, and in some cases the autofocus may not operate correctly. If the lens or camera contacts get dirty, please clean them very gently with a clean, dry cloth. CAUTION
Precautions on cleaning contacts: - Do not wipe the contacts with a wet cloth. It could cause malfunctions.
- Do not touch the contacts directly with your hands. Touching them with your hands could cause corrosion, which would cause the camera to become inoperable.
- When cleaning the contacts on the lens side, be careful not to damage the lens surface.
- If the contacts are particularly dirty, please contact the nearest Canon Service Center.
Securely mounting the lens the camera and the lens mutually exchange information. For this reason, if the lens is not securely mounted, there may be cases where the autofocus does not operate correctly. Please mount the lens securely, as shown in the image below.
 How to Check the [C.Fn2: Custom Controls] Custom Function Setting If autofocus does not operate when the shutter button is pressed halfway, the Custom Function setting may be changed as follows. The diagram below shows the setting for performing only metering (without using the autofocus) when the shutter button is pressed halfway.
 The diagram below shows the setting for using AE lock (to fix the exposure) when the shutter button is pressed halfway.
 In situations like these, change the settings as shown in the diagram below to use Metering and AF start when the shutter button is pressed halfway.
 Please see the Instruction Manual that is supplied with your camera for details about how to change the setting. If you have checked all of the items listed above, but there is still no improvement, please contact the nearest Canon Service Center. Note that, if you are experiencing trouble with a lens made by another manufacturer, you should contact manufacturer of that lens instead. | 