This product is compatible with many camera with the standard hot shoe (such as Canon, Nikon, Pentax, Olympus etc.) Power Management Switch to the ON, the flash will start charging (the charging indicator is dim). After several seconds, the charging indicator turns red and TT520 is ready to shoot. For a test flash, press the test button. After use, press the ON/OFF to OFF to power off. ? If the red charging indicator lamp flickers in every 1s, it indicates low battery. In such case, the power will turn off automatically and you need to replace the batteries 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 Press the MODE key to M Mode. In this mode, you can set TT520 On to your camera hot shoe or speedlite trigger hot shoe to trigger the flash unit. When shooting, adjust the flash power and press the camera shutter, the flash light will flash under the camera synchronous signal. S1 Mode Press the MODE key to S1 Mode. The Mode is applicable for slave flash in order to create many lighting effects. It is respectively applicable for manual flash environment. ? When the flash is S1 mode, it will fire synchronously when the master flash fires, comparable with the effect by the use of radio trigger. ? S2 Mode Press the MODE key to S2 Mode. The mode is applicable for slave flash in order to create many lighting effects. It is respectively applicable for TTL flash environment. The flash unit won"t flash synchronously with the first flash but the second flash from the master flash. ? Power-saving Function To save battery power, the flash will enter stand-by state in about 30 minutes of idle use.