Canon EOS REBEL T6i Instruction Manual page 145

Under [54: Custom Functions (C.Fn)], if you set [9: Mirror lockup] to

[1: Enable], the [Anti-flicker shoot.] setting will automatically switch to
[Disable].
If the subject is against a dark background or if there is a bright light in

the image, flicker may not be detected.
Under certain special types of lighting, the camera may not be able to

reduce the effects of the flicker even when <G> is displayed.
Depending on the light source, flicker may not be detected properly.

If you recompose a shot, <G> may appear and disappear

intermittently.
Depending on the light sources or shooting conditions, expected result

may not be obtained even if you use this function.
Taking test shots is recommended.

If <G> is not displayed in the viewfinder, under [52: Viewfinder

display], set [Flicker detection] to [Show] (p.63). When the camera
reduces the effects of the flicker when you shoot, <G> will light.
Under a light source which does not flicker, or if no flicker is detected,
<G> will not be displayed.
If [Flicker detection] is set to [Show] and [Anti-flicker shoot.] is set to

[Disable], metering under a flickering light source will cause <G>
to blink in the viewfinder as a warning. Setting [Enable] before shooting
is recommended.
In Basic Zone modes, <G> will not be displayed, but the effects of

flicker will be reduced when you shoot.
Anti-flicker shooting also works with flash. However, the expected result

may not be obtained during wireless flash shooting.
3 Reducing FlickerK
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