Here’s a quick quiz: what’s wrong with the following picture?

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Well, its not so much with the picture, which is of the closing ceremony from the Bejing Olympic Games. Its more to do with the audience. See those flashes of light coming from the crowd? They are people in the audience taking photos of the ceremony. The light is coming from their camera’s flash. These people have no idea how to use their flash. Why? Read on.

Why Use Flash?

The word photography comes from two Greek words meaning “painting with light”. When there is not enough light, cameras struggle to create an image. They can compromise by increasing the sensor sensitivity, causing increased noise, by prolonging shutter times, causing motion blur or increasing aperture.

A flash on your camera means that you can bring your own light to any situation. The flash sparks for a very short time, coinciding with the opening of the shutter, and increasing the amount of light the camera can work with.

However, to get good results with a flash, either on camera, or external, understanding some simple principles can greatly improve your images.

The Inverse Square Law

Imagine the flash as a spatter gun. The gun contains a small amount of paint, and shoots it at the scene. The further away the subject is from the flash, the less paint will get to the subject. If you double the distance from subject to flash, the amount of paint reaching the subject is just one quarter. This is because the paint is spread out over an area, which is related to the square of the distance.

What this means is that the amount of effective light from a flash drops very quickly the further you move the subject from the flash. After a certain distance, almost no flash light reaches the subject and the flash becomes useless.

That’s why using flash in a huge scene such as the Olympics is useless. Worse than useless - it tricks your camera into thinking there is enough light - these people will be sadly disappointed with their images.