Definition
What is a neutral-density filter?
A neutral-density, or ND, filter is a gray filter placed in front of or behind a lens to reduce light reaching the sensor while aiming to preserve the scene’s color balance.
ND filters are measured in stops or optical density. By cutting light, they let a crew use a wide aperture for shallow depth of field or a conventional shutter for natural motion blur in bright locations without overexposing the image.
Fixed NDs, variable NDs, and built-in camera NDs have different practical behavior. Variable filters can be convenient but may cause uneven polarization artifacts at strong settings; high-quality fixed filters tend to be more predictable. Any ND should be tested for color cast, flare, and unwanted reflections.
Example in the edit
At midday, a filmmaker adds a six-stop ND so a 24 fps interview can stay at 1/48 second and f/2 instead of closing the lens down dramatically.
Why editors use it
ND filtration preserves creative control of aperture and motion when available light is too bright for the desired camera settings.
Quick answers
Frequently asked questions about Neutral-density filter
Does an ND filter change depth of field?
Not directly. It reduces light, allowing the operator to choose a wider aperture that can create shallower depth of field.
What does a six-stop ND do?
It reduces the transmitted light by six stops, or to roughly one sixty-fourth of its original amount.
Is a variable ND always suitable for video?
It can be useful, but test it. Some models show color shifts or cross-pattern artifacts at strong settings or with very wide lenses.