Canon Speedlite 600 EX-RT User Manual (en, zh)

Using E-TTL II and E-TTL Autoflash in the Shooting Modes
EOS digital cameras have three sizes of image sensors, and the effective 
focal length of the mounted lens varies depending on the model. This 
flash automatically recognizes the image sensor size of each EOS digital 
camera, and automatically adjusts the optimum flash coverage for the 
effective focal length of the lens in a range of 20 to 200 mm.
When mounted on a supported camera, <S> is displayed on the LCD panel.
This function optimizes the white balance during flash shooting by 
transmitting the color temperature information to the EOS digital 
camera when the flash fires. When you set the camera’s white balance 
to <A> or <Q>, the function is enabled automatically.
See the Specifications in your camera’s instruction manual to find out if 
it is compatible with this function.
When autofocus cannot achieve focus on the subject in low-light or when 
contrast is low, the built-in AF-assist beam activates automatically to help 
autofocus.The AF-assist beam in 600EX-RT/600EX is compatible with all 
EOS cameras’ AF points. The AF-assist beam is compatible with 28mm 
and longer focal lengths and its effective range is shown in the table below.
About Auto Zoom Adjustment to Image Sensor Size
About Color Temperature Information Transmission
About AF-Assist Beam
Effective Range (Approx. m/ft.)
0.6 / 2.0 to 10 / 32.8
0.6 / 2.0 to 5 / 16.4
Auto zoom adjustment for image sensor size can be disabled (C.Fn-09/p.98).