Here we’ll take a look at taking pictures using i-TTL flash control, a flash control mode in which light from the flash entering the camera via the lens is used to automatically calculate flash output.
Step 1: Select Remote flash control for Wireless
Step 2: Select Group flash for Remote flash control.
Step 3: Select Group flash options and choose a
flash control mode and flash level for the units in each
Step 4: To select i-TTL as the flash control mode, set the flash control mode for Group A (the flash unit’s current group) to TTL in the group flash options dialog.