Neutral-density Filters for DSLR Cameras

Neutral-density filters are used to reduce the amount of light reaching the sensor. These filters come in both graduated and solid styles and can make the difference between getting a shot that has harsh lighting and contrast or missing out on the opportunity altogether.

A graduated neutral density, or grad, is used to reduce the difference in light range between bright and shadow areas of a scene. In the following first figure, you can see that in order to capture detail in the ground, the sky details are blown out with very little detail. Using a two-stop grad, I've darkened the sky by two stops without affecting the foreground at all, letting me capture more sky detail (second figure).

Tip: You can use a polarizer as a neutral-density filter, too. Doing so gives you as much as two stops of exposure latitude when adjusted for maximum effect.

The other type of neutral-density filter is solid and is used to extend the exposure for things like blurred water image. You can get these in different strengths.