Canon EOS REBEL T6S Instruction Manual page 391

Flash exposure compensation cannot be set for the
external Speedlite.
If flash exposure compensation is set with the external Speedlite, flash

exposure compensation cannot be set with the camera. When the
external Speedlite's flash exposure compensation is canceled (set to 0),
flash exposure compensation can be set with the camera.
High-speed sync cannot be set in the <f> mode.
Under [z1: Flash control], set [Flash sync. speed in Av mode] to

[Auto] (p.184).
The camera makes a small noise when it is shaken.
A small noise may be heard when the camera's internal mechanism

moves slightly.
The shutter makes two shooting sounds during
Live View shooting.
If you use flash, the shutter will make two sounds each time you shoot

(p.203).
During Live View or movie shooting, a white <s> or
red <E> icon is displayed.
It indicates that the camera's internal temperature is high. If the white

<s> icon is displayed, the still photo's image quality may deteriorate.
If the red <E> icon is displayed, it indicates that the Live View or
movie shooting will soon stop automatically (p.230, 268).
Troubleshooting Guide
391