Canon SPEEDLITE EL-1 Advanced User's Manual page 45

Color Temperature Information Transmission
This function optimizes the white balance during flash photography by transmitting the color
temperature information to the EOS DIGITAL camera when the flash fires. When you set the
camera's white balance to < > < > < >, the function is enabled automatically.
Refer to the specifications in your camera's Instruction Manual to find out if it is compatible
with this function.
45