Canon EOS Rebel XS Instruction Manual page 21

Using AF to Focus*
With Live mode, AF can fall to achieve focus in the foIRowing
c_s_s_
Low-contrast subject such as a blue sky and solid-color su_ces
Subjects in low light.
Stripes and other patterns where there is contrast only in the
honzontal 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.
Subjec_ 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 leaving the camera¸
Autofocusing while the subject is way out of focus.
Soft focus effect is applied with a soft focus lens¸
A special e_cts filter is used¸
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