You can customize Speedlite features to suit your preferences. Do it with Custom Functions.
Custom Function Settings
C.Fn-02-113: Convenient when you want to use the depth-of-field preview button to check the depth of field.
C.Fn-08: If the Speedlite or camera's AF-assist beam is disabled, the AF-assist beam will not be emitted.
C.Fn-14: You can change the information displayed on the LCD panel when the shutter button is pressed halfway. This function can be set only with Type-A cameras.