FLASHES

The above photo illustrates the challenge of photographing animals when using flash. On one end, the artificial light provided from the flash allows an impressive depth of field, as shown by the detail and texture on the plant and all parts of the bird here. But on the other hand, the lighting seems a bit…off. The bird and immediate foreground are well lit, but the background is dramatically darker. This is a common problem with bright flash in dim conditions and is known as the Inverse Square Law.

Inverse Square Law

As the distance (measured in meters) from the light increases between the flash and the subject, the amount of light reaching the subject is 1/distance squared (1/d2). That is, in going from 2 to 4 meters from the subject, you are going from 1/4th to 1/16th of the original amount of light reaching the subject. This is a huge drop off in light and results in dark backgrounds. Don’t worry about the math and the calculations – the main point is that light falls off VERY quickly.

So, the way it affects your photo is simple. If you have a bird in front of some vegetation in the background, the light reaching the bird is much brighter than the background. Even if the vegetation is only a few feet behind the bird, it will be much darker because of this square law and light.