So at ISO 1600, we would only need six foot-candles of light (all the other settings being the same), and at ISO 3200 we would need just three foot-candles. Conversely, at ISO 400 we would need about ...

Understanding how the three elements of exposure work — aperture, shutter speed, and ISO — and how to use them will help you master your digital camera.

For example, an exposure of 1/25 sec at f/16, ISO 100 is equivalent to an exposure of 1/400 sec at f/2.8, ISO 100. Because the shutter speed has been reduced by four stops (1/25 ...