Choose a variable ND filter if you move between bright and changing light and want one filter on the lens, and choose a set of fixed ND filters if you value consistent colour and image quality above speed. Both do the same job: they cut light so you can keep a slow shutter speed and a wide aperture in daylight.
Why Video Shooters Use ND Filters
Video usually looks most natural when the shutter speed is about double the frame rate, for example 1/50 at 24 frames per second. In bright sun that setting overexposes the frame unless you close the aperture or lower the ISO to its floor. An ND filter lets you hold the shutter angle and keep the depth of field you want.
How Each Type Works
A fixed ND filter has one strength, such as ND8 or ND64, and does nothing else. A variable ND uses two polarizing layers that you rotate against each other to change the darkness across a range, often marked from a few stops to several stops.
- Fixed ND: one density per filter, so you carry several.
- Variable ND: one filter, adjusted by turning the outer ring.
Key Differences
| Trait | Variable ND | Fixed ND |
|---|---|---|
| Speed of adjusting | Fast, turn the ring | Slow, swap the filter |
| Colour consistency | Can shift at extreme settings | Usually more consistent |
| Cross pattern at the darkest end | Possible, especially on wide lenses | Not an issue |
| Items to carry | One | Several |
Because a variable ND relies on polarizing layers, some designs show a dark X-shaped band or uneven tone when set near maximum, mostly with wide angle lenses. Better made filters limit this, and many include a hard stop to prevent the worst setting. Check the maker’s notes for the exact range of each model.
Choosing for Your Kind of Shooting
- Choose variable ND for documentary work, travel, weddings and any run-and-gun situation where the clouds keep moving.
- Choose fixed ND for planned scenes, interviews, product shoots and cinematic work where you match shots across several cameras.
- Think about your lens collection. A variable ND in a large thread size can be fitted to smaller lenses with step-up rings.
- Think about wide lenses. They show variable ND flaws more easily, so fixed filters are often a safer choice there.
A practical approach is to use a general rule: set the shutter first, then the aperture for the look, then add just enough ND to reach a good exposure. Treat any figures here as rough guidance and adjust to your scene.
Practical Tips
- Set white balance manually, since some ND filters add a slight colour tint.
- Check focus after fitting a filter, because a thick glass layer can make autofocus hesitate in dim conditions.
- Keep a lens cloth handy; large flat glass collects fingerprints quickly.
- If you shoot on a camera with built-in ND, you may not need an external filter at all.
FAQ
Can I use a variable ND for photography too?
Yes, and it works well for long exposures of water or clouds, though a fixed filter is often preferred when you want the most consistent colour across a series of frames.
How many stops of ND do I need for video?
It depends on the light and your aperture. Bright midday sun with a wide aperture often calls for a strong filter in the range of ND32 to ND64, while cloudy days may need far less. Begin with a middle value and adjust.
The Short Version
Variable ND wins on speed and simplicity, while fixed ND wins on consistency and image quality. If your light changes constantly, choose variable; if you plan each shot, choose fixed. Many video shooters carry one of each.
