The humble camera flash has a long history.
Cameras have been recording images for more than 150 years, and for much of that time photographers have needed artificial light to aid in the exposure of their art. The flashes that many people take for granted today are the result of generations of experimentation and innovation. Each major advance in camera flashes borrowed from the previous generation, eventually resulting in the flash on your home camera.
Earliest Flashes
In the earliest days of photography, the only alternative to sunlight was a pan of magnesium powder. Magnesium, which is highly flammable, burned very quickly with a bright flash of light. This powder had to be manually ignited by the photographer just as the photograph was taken. Because the powder was exposed, photographers could be badly burned if too much was used or if the pan tipped over as the magnesium was ignited.
Flash Bulbs
Flash bulbs were developed due to the unsafe nature of loose magnesium powder. These glass bulbs contained magnesium filaments in a glass bulb, which was filled with pure oxygen. When the filaments were ignited electrically they burned incredibly rapidly in the oxygen, producing a bright flash. These flash bulbs could only be used once, but they eliminated the danger of photographers being burned. Later, flash bulbs were covered in a blue coating to better simulate natural sunlight.
Multiple-Use Flashes
Camera companies such as Kodak began experimenting with multiple-use flashes in the 1960s. The flashcube contained four separate flashes, each ignited electrically by a sensor on the camera's shutter. Each small flash had a mirrored surface behind the flash bulb to focus all of the light in a single direction, allowing the flash bulb to be greatly reduced in size. This concept was later adapted into strip flashes, which contained ten or more flashes in a single unit. These multiple-use flashes allowed photographers to take more photos without worrying about constant flash replacement.
Modern Flashes
Electronic flashes are used in modern cameras, which can be used thousands of times without needing to be replaced. These flashes are filled with xenon gas, across which an electric spark is passed to produce a brief, brilliant flash of light. Modern flashes still employ a mirrored backing to keep the size small, and are often built into consumer cameras. Professional flashes are available in different intensities and are usually separate units that are attached to the camera as needed by the photographer.
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