Neutral Density (ND) filters are often overlooked by photographers, yet they offer a range of practical uses and can help achieve results that would otherwise be difficult or impossible.

ND filters look grey and reduce the amount of light reaching the film or sensor. They do not affect colour balance.

They are commonly used for four main purposes:

• To allow slower shutter speeds, particularly with fast films, so movement can be captured in subjects such as waterfalls, clouds, cars and the sea.
• To reduce depth of field by enabling wider apertures, helping separate the subject from the background.
• To lower the effective ISO of high-speed film (that is, above ISO400), allowing it to be used outdoors in bright conditions.
• To enable cine and video cameras, which have fixed shutter speeds, to film bright scenes such as snow, sand or other high-light situations that would otherwise cause overexposure.