Flash units work by means of a capacitor charged by battery. When triggered, the capacitor releases its full charge instantaneously from the flash tube, ionizing the gas inside. Concentration of the light output depends on how large the capacitor and on the square in the voltage at which the product operates, and is normally quoted as the guide number.
The restrictions of full flash illumination are the types of frontal lighting. Put simply, the lighting is almost shadowless and it also falls off equal in proportion on the distance from the camera. A common purely flash-lit photograph is likely to feature flat illumination over the main subject and a dark background. The result is clear, sharp, and with good color separation, but is usually missing in ambiance. Typical good purposes of full-on flash are close-ups of colorful subjects, simply because … Read the rest