This product is compatible with many camera with the standard hot shoe (such as Canon, Nikon, Pentax, Olympus etc.)Power Control The flash unit has 8 steps of power output control which indicated by 8 pieces of LED lamp for different level. Press "+" to make power higher and they are 1/128,1/64,1/32,1/16,1/8,1/4,1/2,1/1. Otherwise, press "-" to make power lower. M Mode S1 Mode S2 Mode Power-saving Function To save battery power, the flash will enter stand-by state in about 30 minutes of idle use. In S1/S2 mode, the flash will enter stand-by state in about 60 minutes of idle use. Press any button to wake it up. In Power-saving mode, the charging indicator flickers in every 3 seconds. Other Indicators are turned off. Protection Function Protection in continuous flashes:To prevent the flash head from getting too hot and damage, please do not flash over 20 times when in power lever 1/2,1/1. Please cool down the flash unit for at least 10 minutes. The over-temperature protection function will be activated if you continue to flash after 20 times. In this state the charging time will turn to 10-25s. Please cool down the flash unit around 10 minutes and it will turn to normal state. Systematic over-temperature protection:When the inner circuit is over-heating, which indicates over use of the flash unit, the inner circuit will shut down power automatically. The flash unit will turn to normal state after the inner circuit is cooled down. Color Temperature: 5600K+200K Flash Duration :1/800s~1/2000s Dimensions :190*75*55mm Net Weight :286g 1 X New TT520 Speedlite