Flash (photography)

A flash is a device used in photography that produces a brief burst of light (lasting around 1⁄200 of a second) at a color temperature of about 5500 K[1][citation needed] to help illuminate a scene.

Studies of magnesium by Bunsen and Roscoe in 1859 showed that burning this metal produced a light with similar qualities to daylight.

The potential application to photography inspired Edward Sonstadt to investigate methods of manufacturing magnesium so that it would burn reliably for this use.

With the help of engineer William Mather, who was also a director of the company, they produced flat magnesium ribbon, which was said to burn more consistently and completely so giving better illumination than round wire.

A measured amount was put into a pan or trough and ignited by hand, producing a brief brilliant flash of light, along with the smoke and noise that might be expected from such an explosive event.

His patent describes a device for igniting photographers' flash powder by using dry cell batteries to heat a wire fuse.

The use of flash powder in an open lamp was replaced by flashbulbs; magnesium filaments were contained in bulbs filled with oxygen gas, and electrically ignited by a contact in the camera shutter.

A later innovation was the coating of flashbulbs with a plastic film to maintain bulb integrity in the event of the glass shattering during the flash.

There was a significant delay after ignition for a flashbulb to reach full brightness, and the bulb burned for a relatively long time, compared to shutter speeds required to stop motion and not display camera shake.

Slower shutter speeds (typically from 1⁄10 to 1⁄50 of a second) were initially used on cameras to ensure proper synchronization and to make use of all the bulb's light output.

Other flashbulbs in common use were the M-series, M-2, M-3 etc., which had a small ("miniature") metal bayonet base fused to the glass bulb.

In 1965 Eastman Kodak of Rochester, New York replaced the individual flashbulb technology used on early Instamatic cameras with the Flashcube developed by Sylvania Electric Products.

The spring struck a primer tube at the base of the bulb, which contained a fulminate, which in turn ignited shredded zirconium foil in the flash.

The Flipflash name derived from the fact that once half the flashbulbs had been used, the unit had to be flipped over and re-inserted to use the remaining bulbs.

In many Flipflash cameras, the bulbs were ignited by electrical currents produced when a piezoelectric crystal was struck mechanically by a spring-loaded striker, which was cocked each time the film was advanced.

[15] Electronic flash, often called "strobe" in the US following Edgerton's use of the technique for stroboscopy, came into some use in the late 1950s, although flashbulbs remained dominant in amateur photography until the mid 1970s.

Towards the end of the 1960s electronic flashguns of similar size to conventional bulb guns became available; the price, although it had dropped, was still high.

Ring flashes that fit to a camera's lens can be used for shadow free portrait and macro photography; some lenses have built-in ring-flash.

The strength of a flash device is often indicated in terms of a guide number designed to simplify exposure setting.

These are commonly used by scientists or engineers for examining extremely fast-moving objects or reactions, famous for producing images of bullets tearing through light bulbs and balloons (see Harold Eugene Edgerton).

This information can be manipulated to suppress or enhance details or capture the intricate geometric features of a scene (even those hidden from the eye), to create a non-photorealistic image form.

Unlike xenon tubes, LEDs require only a low voltage, eliminating the need of a high-voltage capacitor.

The LED flash can also be used for illumination of video recordings or as an autofocus assist lamp in low-light photography; it can also be used as a general-purpose non-photographic light source.

In the past, slow-burning single-use flash bulbs allowed the use of focal-plane shutters at maximum speed because they produced continuous light for the time taken for the exposing slit to cross the film gate.

For example, the Mecablitz 58 AF-1 digital flash unit has a guide number of 58 in normal operation, but only 20 in HSS mode, even at low speeds.

It is also possible to use one's own palm for that purpose, resulting in warmer tones on the picture, as well as eliminating the need to carry additional accessories.

Wireless radio transmitters, such as PocketWizards, allow the receiver unit to be around a corner, or at a distance too far to trigger using an optical sync.

[24] Using on-camera flash will give a very harsh light, which results in a loss of shadows in the image, because the only lightsource is in practically the same place as the camera.

In crowds at sports matches, concerts and so on, the stands or the auditorium can be a constant sea of flashes, resulting in distraction to the performers or players and providing absolutely no benefit to the photographers.

It can be somewhat reduced by using the "red eye reduction" found on many cameras (a pre-flash that makes the subject's irises contract).