Meike Mk-320s TTL Speedlite for Sony a7 a7ii a7s Mi Hot Shoe Camera with Free Diffuser Built-in highlight LED: light provides the auxiliary lighting for the video clips TTL function: TTL full-automatica flash is to automatically adjust the flash intensity of the flash lamp for the correct flashing according to the feedback signal from the photometry of the camera lens High precsion manual adjustment: 8 Power levels, each level has 3 fine tuning adjustment, providing you a more precise brightnessoutput and flexible brightness control Strobpscopic flash function: The strobosopic flash is to record the continuous motion of the subject in a picture in virtue of the continuous flash of the electronic flasher S1/S2 mode S1 mode: It is suitable for the manual mode and when the master control flashlight is on, the remote control flashlights will be triggered; S2 mode:It is suitable for the master TTL mode, and only when the second flash of the master control flashlight is present can the remote control flashlights be triggered