Subjects Difficult To Focus; Mf: Manual Focusing - Canon EOS Rebel T4i 18-135mm IS STM Lens Kit Instruction Manual

Subjects Difficult to Focus

Autofocus can fail to achieve focus (viewfinder's focus confirmation light
<o> 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 either 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.61).
(2) Set the lens focus mode switch to <MF> and focus manually.
For subjects difficult to focus during Live View shooting with [u+Tracking],
[FlexiZone - Multi], or [FlexiZone - Single], see page 159.

MF: Manual Focusing

Focusing ring
If you hold down the shutter button halfway during manual focusing, the AF
point achieving focus will light up briefly in red, the beeper will sound, and
the focus confirmation light <o> in the viewfinder will light up.
100
Set the lens focus mode switch to
1
<MF>.
Focus the subject.
2
Focus by turning the lens focusing
ring until the subject looks sharp in
the viewfinder.