Canon EOS Rebel T4i 18-135mm IS STM Lens Kit Instruction Manual page 325

I cannot set flash exposure compensation with [External
flash func. setting].
If flash exposure compensation has been set on an external Speedlite,
[Flash exposure compensation] (p.217) cannot be set in the
[External flash func. setting] screen. Also, if you set flash exposure
compensation with the camera and then set flash exposure
compensation with the external Speedlite, the Speedlite's flash
exposure compensation setting will be given priority. When the
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.215).
The camera makes a noise when it is shaken.
The built-in flash's pop-up mechanism moves slightly. This is normal.
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.145).
During Live View and 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.165, 195).
Troubleshooting Guide
325