A flash is a device employed in photography manufacturing a flash of synthetic light at a color temperature of about 5500 K to help illuminate a scene. A major point of a flash is to illuminate a dark scene. Another uses are capturing quickly moving objects or changing the standard of light. Flash refers either to the flash of the electronic or light itself to flash unit discharging the light. Most flash units as of 2009 are electronic, having developed from single-use flashbulbs and combustible powders. Modern cameras frequently turn on flash units mechanically.

Flash units are typically built straight into a camera. Some cameras permit separate flash units to be mounted through a standardised "accessory mount" bracket (hot shoe). In pro studio equipment, flashes might be giant, stand-alone units, or studio strobes, powered by special battery packs or hooked up to mains and synchronized with the camera from either a flash synchronization wire, radio transmitter, or are light-triggered, meaning that only 1 flash unit should be synchronized with the camera, which triggers the other units.

Flash units are split into two classes: Internal in-built flash units or external flash units. Internal flash units are built into the camera. Nearly all digital cameras include such a unit and permit the user some control of it through the camera's menus and buttons. The attachment of external flash units to a camera's body is done through a dedicated slide-in slot or by utilizing an electric wire. Not all digicams support external flash units. Sometimes the bottom pocket cameras don't permit external flash units while all high end digital SLR cameras do permit such external flash units. External flash units can change a lot. They can have various light energy levels that they can emit and various mechanical traits. Some external flash units also include smart sensors to determine background light, distance and other optical parameters so as to optimize the flash effect.

Digital cameras can use their flash units in automated or in manual mode. In automated mode the camera measures background light and fires the flash when not enough background light is available. Infrequently the camera will make the incorrect call as to using the flash and will either fire or not fire the flash when the opposite was required. Setting the flash force is vital too. If the flash unit fires too much light energy on things that are too near to the camera the digital photograph will be washed out. From a different perspective if the flash unit fires a touch of light energy on an object that's further away from the digicam the digital photograph will be a too dark.

Flash units have restrictions too. They can't light any scene and any object at any distance from the camera. It's very important to understand your flash unit restrictions. As an instance check what the maximum light energy that it can emit is and what the farthest that an object can be effectively lit from. If the thing is out of the effective flash range it is really better to switch off the flash altogether and employ a tripod with a longer exposure. Occasionally it is helpful to use the flash regardless of if there's enough background light. In such cases you can by hand force the camera to launch the flash.