Canon EOS Rebel T3i 18-135mm IS Lens Kit EOS REBEL T3i / EOS 600D Instruction - Page 87

Subjects Difficult to Focus Autofocus can fail to achieve focus (viewfinder's focus confirmation light blinks) with certain subjects such as the following: Very low-contrast subjects. (Example: Blue sky, solid-color walls, etc.) Subjects in very low light Extremely backlit or reflective subjects (Example: Car with a highly reflective body, etc.) Near and far subjects covered by an AF point (Example: Animal in a cage, etc.) Repetitive patterns (Example: Skyscraper windows, computer keyboards, etc.) In such cases, do one of the following: (1) With One-Shot AF, focus an object at the same distance as the subject and lock the focus before recomposing (p.53). (2) Set the lens focus mode switch to and focus manually. For conditions where AF can fail to achieve focus with [Live mode]/[u Live mode] during Live View shooting, see page 134. MF: Manual Focusing 1 Set the lens focus mode switch to . Focusing ring 2 Focus the subject. Focus by turning the lens focusing ring until the subject looks sharp in the viewfinder. If you hold down the shutter button halfway during manual focusing, the AF point achieving focus will light in red briefly, the beeper will sound, and the focus confirmation light in the viewfinder will light. 87