The YN-622C? Yongnuo ETTL Flash utilizes a series of LEDs to display settings and allow users to make adjustments. On the device is also an AF assist beam to help in low-light conditions. Multiple sync modes are available for more specific needs or effects, including 1st and 2nd curtain sync. A high speed sync mode is available when a flash is connected via the PC sync port and will help in bright lighting conditions and for stopping motion with a maximum speed of 1/8000 second. Additionally, the transceivers run on 2 AA batteries each.