Difficult subjects for AF (Auto Focus) (EOS REBEL T3i/EOS 600D)
09-Feb-2011
8201001300
Solution
AF (Auto Focus) can fail to achieve focus (the focus confirmation light blinks) on certain subjects such as the following:
- Low-contrast subjects. (ex. blue sky, solid-color walls, etc.)
- Subjects in low light.
- Extremely backlit reflective subjects. (ex. car with a reflective body)
- Overlapping near and far objects. (ex. animal in a cage)
- Repetitive patterns. (ex. Skyscraper windows, computer keyboards, etc.)
In such cases, do either of the following:
- Focus on an object at the same distance as the subject and lock the focus before recomposing (For information on the focus lock, please refer to the following note and the Related information section).
- Set the lens focus mode switch to <MF> and focus manually.
NOTE
With [One-Shot AF], while you press the shutter button halfway to focus a still subject, the focus will be locked. You can then recompose the shot and press the shutter button completely to take the picture. This is called "focus lock". For further information, please refer to the Related Information section. (In the < 
> (Sports) mode, AF mode is set to [AI Servo AF] automatically.)
> (Sports) mode, AF mode is set to [AI Servo AF] automatically.)