Flash (photography)

A flash is a special device used in photography that creates a quick burst of light, lasting about 1⁄200 of a second. This burst of light has a color temperature of around 5500 K, which helps make a scene brighter, especially when it is dark. The main reason people use a flash is to light up areas that are too dark, but it can also be useful for taking pictures of things that move very fast or for changing how the light looks in a photo.

The word flash can mean either the bright light itself or the electronic flash unit that creates the light. Today, most flash units are electronic, but they used to come from single-use flashbulbs and special flammable powders. Many modern cameras have flash units built right into them. Some cameras can also hold separate flash units on a special part called a hot shoe. For professional use, flashes can be big, stand-alone units or studio strobes that get power from special batteries or from the regular electricity supply, known as mains power. These flashes are timed with the camera using a flash synchronization cable, a radio signal, or by using light to trigger them. In this case, only one flash needs to be connected to the camera, and it can then cause other flash units, called slaves, to go off too.

Types

Flash-lamp and flash powder

Main article: Flash-lamp

Studies showed that burning magnesium created light similar to daylight. This idea led to making magnesium for photography. By the 1860s, companies made flat magnesium ribbon that burned better and cheaper than round wire. Later, a mix called flash powder was made from magnesium and potassium chlorate. It made a bright flash but could be dangerous if wet. Electric flash lamps came later, using batteries to heat a wire and ignite the powder.

Flashbulbs

Flashbulbs replaced flash powder. They contained magnesium in bulbs filled with oxygen, ignited by the camera shutter. First made in 1929, they were used once and got very hot. Later, coatings were added to protect the glass, and zirconium replaced magnesium for brighter flashes.

Flashcubes, Magicubes and Flipflash

In 1965, Kodak introduced Flashcubes with four flashbulbs on a module. After each flash, the cube rotated to a new bulb. Magicubes worked without electricity, using springs to ignite the bulbs. Flipflashes gave ten flashes and could be flipped to use the remaining bulbs.

Electronic flash

Electronic flash was introduced in 1931. It flashes almost instantly and very briefly. Early units were big and expensive, but later became smaller and more affordable. Electronic flashes charge a capacitor and release it through a tube for a quick burst of light.

High speed flash

High-speed flashes are used for very fast events, like bullets moving. They can flash in less than a microsecond.

Multi-flash

Cameras can use multiple flashes to find depth in a scene or create special effects.

Flash intensity

Electronic flashes can change their brightness. Smaller units adjust how long the flash lasts, while bigger ones change how much power they use.

Flash duration

Flash duration is how long the light stays bright. It helps freeze motion in photos.

Flash LED used in Phones

Phones use LED flashes. They are smaller, need less power, and can also help with focusing in low light.

Focal-plane-shutter synchronization

Electronic flashes work with cameras that have moving shutters. The flash must sync with the shutter to get a clear picture. Some flashes can fire multiple times to work with very fast shutter speeds.

Technique

Flash can be used when there isn’t enough natural light, or to add extra light in more advanced setups. Basic flash creates strong, direct light, but there are ways to make it softer or create different effects.

Tools like softboxes and diffusers help spread out the light, making it gentler. Reflectors, such as umbrellas or white surfaces, can bounce the light back onto the subject. Bounce flash sends the light up to a ceiling or wall, which then reflects it back, creating softer lighting and reducing harsh shadows. Sometimes, a small bounce card or even the photographer’s hand can help direct some light back to fill in shadows.

Fill flash adds a little extra light to parts of a scene that would otherwise be too dark. The flash is used just enough to brighten the subject while the rest of the scene is lit by natural light. Additional slave flash units can be triggered by the main flash to add light from other directions. Some flashes can also flash several times in quick bursts to capture moving action.

Colored gels can change the shade of the flash to match other lights, like warm tungsten or cool fluorescent lights. Photographers can also manually trigger the flash at any time, separate from the camera’s shutter.

Drawbacks

When using a flash close to the camera, the light can be very strong and harsh. This can wash out shadows in the picture because the flash is almost right where the camera is. To get better results, you can balance the flash with other lights or use the flash away from the camera. You can also use an umbrella or softbox to make the light softer and create better shadows.

Small built-in flashes on cameras often don’t have enough power to light up things far away—usually more than about 3 metres (10 feet). This can make pictures look dark and grainy. Bigger flashes, like those used in studios, can light up larger areas and even work against sunlight up close. Sometimes cameras will flash even when the subject is far away, which doesn’t help and can be distracting, especially in places like sports events or concerts.

Another common issue is the “red-eye effect,” where people’s eyes look red in pictures because the flash is too close to the camera lens. This can sometimes be reduced with a feature called “red-eye reduction” on cameras, which flashes a little light before the main flash to make pupils shrink. The best way to avoid red-eye is to use a flash that is far from the camera or bounce the flash off a wall or ceiling.

Some cameras take a quick test flash before the real one, which can cause people to blink or close their eyes just as the picture is taken. More expensive cameras may have a feature to avoid this. Flash can also be distracting to people, and some places like museums may not allow it. Setting up flash equipment can take time and needs to be done carefully to keep it secure.