The Built-in Flash Fires a Series of Flashes before a Picture is Taken (EOS REBEL T6/EOS 1300D)
Solution
In dimly lit shooting conditions, pressing the shutter button halfway may trigger the built-in flash to fire a series of flashes to assist autofocusing. This is called AF-assist beam.
The AF-assist beam can be turned off in the Creative Zone modes.
NOTE
The AF-assist beam will be emitted when necessary when the Mode Dial is set to < 
>< 
>< 
>< 
>< 
>< 
>.
>< >< >< >< >< >.The procedure for turning off the AF assist beam is explained below.
1. Set the camera’s power switch to <ON>.
2. Set the Mode Dial to a Creative Zone mode.
3. Press the <MENU> button to display the menu screen.
4. Press the < 
>< 
> buttons to select the [ 
] tab.
>< > buttons to select the [ ] tab.Press the < 
>< 
> buttons to select the [Custom Functions (C.Fn)], then press < 
>.
>< > buttons to select the [Custom Functions (C.Fn)], then press < >.
5. Press the < >< > buttons to select [7], then press < >.
>< > buttons to select [7], then press < >.
6. Press the < >< > keys to select [1:Disable], then press < >.
>< > keys to select [1:Disable], then press < >.・ At the bottom of the screen, the current Custom Function settings are indicated below the respective function numbers.
7. Press the <MENU> button. The screen below will reappear.
8. Press the <MENU> button again to return to the shooting screen.
NOTE
● To make auto focusing in dimly lit places easier, set the [AF-assist beam firing] to [0:Enable].
● AF-assist beam will not be emitted from the built-in flash in < 
>, < 
>, or < 
> mode, or when [Built-in flash firing] is set to < 
> in < > or < > mode.
>, < >, or < > mode, or when [Built-in flash firing] is set to < > in < > or < > mode.● The AF-assist beam cannot be emitted with AI Servo AF operation.
● The effective range of the AF-assist beam emitted by the built-in flash is approx. 4 meters/13.1 feet.