In photography, any method of producing better lighting of the object you’re photographing by using an instant and short burst of light is known as a flash. Using a flash makes it possible to take pictures with sharp quality even in poor lighting conditions. Most cameras come with an integrated flash or a port capable of connecting to an external flash. In photo studios, complex flash systems are used in order to achieve optimum illumination to ensure high-quality results.
In 1861, the chemist and photographer Eduard Liesegang was the first to use ignited magnesium as a source of light when photographing. Later, this method was used to develop the first flash powder; this substance was very unstable and difficult to control, which is why its use often led to accidents. In the 1930’s, the engineer Harold Edgerton invented the first electronic flash unit and thus laid the foundations for later developments in flash technology.
The way a flash works is actually quite simple. Immediately when the shutter release is pressed, a short flash of light is triggered which is reflected off of the object being photographed. The time between pressing the shutter release button and the reflection of the light off of the object has to be coordinated with the shutter speed of the camera. The shutter should be fully open when the flash triggers. This is the only way the short flash of light can be optimally used when taking pictures.
Besides just using the flash to better illuminate the object being photographed, it can also be used along with various methods in order to produce certain effects and moods in the photo. When this is done, it makes a big difference if the flash is used as a main source of light, as a supplement to light already present or if the flash is discharged either directly or indirectly at the object. The red-eye effect that appears in many photos shot with a flash, for example, can be reduced when using a pre-flash.
Furthermore, the light colour of the flash, which is expressed in degrees Kelvin, influences the colour temperature in the photo. Modern photos and flashes usually use a white light since it is neutral and doesn’t distort the natural colours of the object when photographing.
The range and coverage of a camera’s flash is given as a guide number. This number tells you the luminous energy of the flash, which is calculated from the distance between the flash and the object in metres, and the necessary f-number to use in order to ensure optimal illumination.
When using a flash, it’s possible that strong contrasts between light and shadows or disturbing reflections might appear. That’s why a diffuser is often used in professional photography, which spreads the light from the flash. This makes the light produced from the flash softer and disturbing effects in the photo are reduced. Basically any kind of transparent or colour-neutral material can be used to spread out the light from the flash. Thus, things like white screens, nylon fabric, Plexiglas, or even greaseproof paper are often used in flash photography.