Canon EOS Rebel T2i EOS REBEL T2i / EOS 550D Instruction Manual - Page 117

Using AF to Focus Shooting conditions which can make focusing difficult: Low-contrast subjects such as the blue sky and solid-color, flat surfaces. Subjects in low light. Stripes and other patterns where there is contrast only in the horizontal direction. Under a light source whose brightness, color, or pattern keeps changing. Night scenes or points of light. Under fluorescent lighting or when the image flickers. Extremely small subjects. Subjects at the edge of the picture. Subjects strongly reflecting light. The AF point covers both a near and faraway subject (such as an animal in a cage). Subjects which keep moving within the AF point and cannot keep still due to camera shake or subject blur. A subject approaching or moving away from the camera. Autofocusing while the subject is way out of focus. Soft focus effect is applied with a soft focus lens. A special effects filter is used. 117