An ND filter is a darkened piece of glass that cuts light evenly, so you can keep a natural-looking shutter speed and a wide aperture when shooting video in bright conditions. Without one, you must raise the shutter speed or close the aperture, which makes motion look choppy or removes the soft background.
Why Video Needs ND
Video usually follows the 180-degree shutter guideline: set the shutter speed to about double the frame rate. At 24 frames per second that means roughly 1/48 second, often rounded to 1/50. In sunlight that exposure is far too bright, and the usual fixes cause problems.
- A fast shutter makes motion look sharp and jittery, with less natural blur.
- A very small aperture can reduce sharpness through diffraction and removes background blur.
- Lowering ISO helps only until the base value is reached.
An ND filter solves the problem by reducing light so the exposure triangle can stay where you want it.
Choosing a Strength
| Conditions | Baseline strength |
|---|---|
| Overcast day or bright interior | 1 to 2 stops |
| Moderate sunlight | 3 stops |
| Bright sun, wide aperture | 4 to 6 stops |
| Strong sun on snow or sand | 6 stops or more |
These are only general guides. Your camera, lens, and chosen aperture decide the actual need.
Step by Step
- Set the frame rate for your project, such as 24, 25, or 30 frames per second.
- Set the shutter speed to about twice the frame rate.
- Set ISO to the camera’s base or native value.
- Choose the aperture for the look you want, such as wide for a soft background.
- Check the exposure. If it is too bright, attach an ND filter and adjust until the exposure meter or zebras look right.
- Keep the filter in place and do not change the shutter speed to fix exposure.
Fixed or Variable
Fixed ND filters offer consistent color and sharpness, but you swap them as the light changes. Variable ND filters let you rotate to change density, which is convenient for run-and-gun shooting. Some cameras have built-in ND, which makes everything easier. With variable filters, watch for dark bands or color shifts at the strongest setting, and avoid wide-angle lenses with them when the problem appears.
Practical Habits
Keep a clean cloth handy, because dust and fingerprints on a filter show up in bright scenes. Match filter sizes to your lens thread, or use step-up rings. Confirm exact specifications on the maker’s page before you buy.
FAQ
Can I use ND filters for photography too?
Yes, for long exposures and wide-aperture portraits in daylight. The same filter works for both.
Do I need a polarizer as well?
Not necessarily. A polarizer reduces reflections and also cuts about one to two stops, so some people use it in place of a light ND filter.
The Short Version
Use an ND filter to hold a natural shutter speed and your preferred aperture in bright light. Choose the weakest strength that gets the exposure right, keep the camera at base ISO, and adjust exposure only with the filter.
