Wireless TTL Slave:
Use the comfort of TTL wirelessly with Canon eTTL and Nikon i-TTL! The YN-565EX serves as a wireless TTL slave which is triggered by a compatible master flash like the Canon 580 EX II or Nikon SB-900, a camera with commander function like Canon 60D or wireless commander like ST-E2. If there is no commander function or master flash it still can be used with TTL on top of a compatible camera. In TTL slave mode 3 groups A, B, C and 4 channels are supported. Please note that the YN-565EX cannot serve as a wireless TTL master and does not support HSS.
Flash Mode Manual, S1, S2:
Many photographers like the manual mode in strobist photography, because it gives them most freedom in composing their pictures. You can adjust the power level from 1/128 to 1/1 in 1/3EV steps. Also you can use the optical slave modes S1 and S2. Which allow optical triggering by other flashes without need of an additional trigger. The S2 mode supresses the TTL metering flash.