Ordinary type Flash is the Flash output power is not adjustable Flash, the Flash Flash nominal index GN is a constant value.
Circuit made up of four parts: oscillation booster part, charging rectifier part, voltage indication and pulse triggers the Flash part. When the power is connected, use the switching characteristics of the transistor V1, forming a blocking, the T1 primary access to an alternating voltage, T1 boost, making it subordinate to get greater than 300V AC voltage. After half-wave rectifier diodes D1, the alternating voltage into DC voltage to the primary trigger capacitance and capacitor C2 C3 charge storage. When the voltage to rated voltage 70%-filled when indicator neon lamp (Ne), and normal Flash indicates the Flash is in wait state. When you press the button AN, triggering circuit (formed by R3 and C3 and T2 and Xe) produces pulsed voltage, subprime-induced moment in T2 high pressure (10kV) pulse through Xe flash tube trigger nitrogen gas ionization in Xe Flash tubes and conduction, stored on the capacitor C2 moments through the Flash discharge of electric energy into light, completed a Flash.
Camera's built-in Flash works as above. When the brightness of the scene is low, the camera's metering system will emit a low light information, manually or automatically by the camera connected and flashes to charge Flash circuit. Some cameras also have automatic control system of Flash content (Auto-Tune flash light) in order to obtain more accurate exposure.