Last updated: October 2026
An ND filter is dark glass that cuts the light reaching your sensor so you can keep a natural shutter speed and a wide aperture in bright conditions. Photo shooters can dodge the problem by raising the shutter speed. Video shooters cannot, because the shutter is spoken for. This explainer covers the science a vlogger needs: the 180-degree shutter rule, stops, fixed vs variable filters, the three artefacts variable NDs are known for, and a five-step test for the filter you already own.
The short version
- Video needs ND because the shutter is locked. At 24fps your shutter sits near 1/50, so in full sun only the filter can remove the spare light.
- A stop halves the light. ND8 is 3 stops, ND64 is 6 stops, ND1000 is 10 stops.
- A normal sunny vlogging day needs about 5 to 6 stops at f/2.8, fewer in shade or near sunset.
- Fixed filters are the accurate ones; variable filters are the fast ones. Solo vloggers usually live with variable and manage its flaws.
- Every variable ND has a usable limit. Past it you get the X-cross, colour casts and infrared contamination. Test yours once and learn where it sits.
On this page
- Why video needs an ND filter when a photo would not
- The 180-degree shutter rule, and when to break it
- Stops explained: what the ND numbers actually mean
- How many stops does a vlogging day need?
- Fixed vs variable ND: the honest trade-off
- The X-cross, colour casts and infrared: variable ND artefacts
- Test the filter you already own
- The shooting routine: set exposure in the right order
- Fixed-aperture cameras: action cams, pocket cameras and phones
- ND filter questions, answered
- Keep exploring
Why video needs an ND filter when a photo would not
A photo balances exposure with three controls: aperture, shutter speed and ISO. Video gives one away, because the shutter speed is fixed by the frame rate to keep motion looking natural. On a bright day that leaves more light than aperture and ISO can handle, and the ND filter removes the excess.
Watch what happens without one. You are filming a walk-and-talk at midday: 24fps, shutter at 1/50 for natural motion blur, lens at f/2.8 so the background melts away, ISO at its base of 100. The image is still two or three stops too bright, and every control is spent: the aperture is the look you want, the ISO cannot go lower, the shutter is committed. The only fix that keeps the look is dark glass.
The tempting shortcut is to raise the shutter speed to 1/1000 and skip the filter. The exposure works, but the footage changes character: each frame becomes razor sharp, so movement turns choppy and strobing, most obvious in walking shots, pans and passing traffic. That jitter is the signature of phone footage shot in hard sun. Our guide to vlogging camera settings explained shows how the shutter, aperture and ISO choices fit together before a filter enters the picture.
The 180-degree shutter rule, and when to break it
The 180-degree rule says your shutter speed should be one divided by twice the frame rate: 1/50 at 24 or 25fps, 1/60 at 30fps, 1/100 at 50fps, 1/120 at 60fps. That ratio gives each frame a natural amount of motion blur, the look audiences read as cinematic.
The name comes from film cameras, whose rotating disc shutter opened for half of each cycle: 180 degrees of a 360-degree rotation. Digital cameras copy the ratio with shutter speed. At 24fps and 1/50, a moving hand blurs slightly across each frame and your eye stitches the frames into smooth motion. Slow the shutter and movement smears; speed it up and movement turns into frozen slices.
| Frame rate | 180-degree shutter speed | What cameras usually show |
|---|---|---|
| 24fps | 1/48 | 1/50 |
| 25fps | 1/50 | 1/50 |
| 30fps | 1/60 | 1/60 |
| 50fps | 1/100 | 1/100 |
| 60fps | 1/120 | 1/120 or 1/125 |
Breaking the rule is a choice, not a sin. A faster shutter suits action you want to look crisp and urgent, and on a locked-off talking-head shot a small deviation is invisible anyway. A slower shutter buys exposure in low light at the cost of smeared movement. Our guide to vlogging frame rates explained goes deeper on how the frame rate itself changes the feel of motion. What matters here: once you pick a shutter for the look, it stops being an exposure control. That is the gap the ND filter fills.
Stops explained: what the ND numbers actually mean
A stop is a halving of light. The ND number is the denominator of the light that gets through: ND8 lets through one eighth (3 stops), ND64 one sixty-fourth (6 stops), ND1000 roughly one thousandth (10 stops). Every doubling of the ND number adds one stop.
Three labelling systems describe the same thing. The ND number (ND8, ND64) is the common one on video filters. Optical density notation counts 0.3 per stop, so an ND 0.9 is a 3-stop filter. Variable filters are sold by range instead: ND2 to ND32 means 1 to 5 stops, while ND8 to ND2000 claims roughly 3 to 11 stops, a figure to treat with suspicion for reasons the artefacts section covers.
| Filter | Stops | Light that gets through | Typical vlogging job |
|---|---|---|---|
| ND2 | 1 | 1/2 (50%) | Golden hour trim |
| ND4 | 2 | 1/4 (25%) | Bright overcast |
| ND8 | 3 | 1/8 (12.5%) | Shade, window light |
| ND16 | 4 | 1/16 (6.25%) | Light cloud at midday |
| ND32 | 5 | 1/32 (3.1%) | Full sun, moderate aperture |
| ND64 | 6 | 1/64 (1.6%) | Full sun, wide aperture |
| ND128 | 7 | 1/128 (0.8%) | Full sun at f/1.8 or wider |
| ND1000 | 10 | 1/1000 (0.1%) | Long exposures, not everyday video |
Stops add when filters stack: an ND8 in front of an ND64 gives 9 stops. The same maths explains why one stop either way rarely rescues a bad choice. Pick the density for the light you actually shoot in, which the next section works out with real numbers.
How many stops does a vlogging day need?
For a typical outdoor vlog at 24fps, 1/50 shutter and base ISO: about 5 to 6 stops in full midday sun at f/2.8, 2 to 3 stops in bright overcast or open shade, and 0 to 2 stops near sunset. A variable filter covering 2 to 7 stops, or a fixed ND64, handles most of a shooting day.
The maths is simple once you do it once. Bright midday sun exposes correctly at roughly f/16 with a 1/50 shutter at ISO 100. You want f/2.8. Count down: f/11, f/8, f/5.6, f/4, f/2.8 is five stops of aperture, and each stop you open must be repaid by the filter because the shutter and ISO stay put. Shoot at f/1.8 and the bill grows to about six and a half stops. That is why the sunny-day answer lands near ND64, and why a hopeful 2-stop filter gets left in the bag all summer.
| Light you are filming in | Working aperture at 1/50, base ISO | Stops to reach f/2.8 | Filter that fits |
|---|---|---|---|
| Full midday sun | About f/16 | 5 | ND32, or ND64 for margin |
| Full sun, lens at f/1.8 | About f/16 | 6 to 7 | ND64 to ND128 |
| Bright overcast or open shade | About f/5.6 | 2 | ND4 |
| Indoors by a large window | About f/8 | 3 | ND8 |
| Golden hour | About f/4 | 0 to 1 | None, or ND2 |
Two adjustments worth knowing. Higher frame rates need less ND, not more: at 60fps your shutter is 1/120, which already removes over a stop of light compared with 1/50. And cloud is a moving target: a day that starts at 6 stops can drop to 3 in minutes. That swing is the practical argument for a variable filter on a walking vlog, whatever its flaws.
Fixed vs variable ND: the honest trade-off
A fixed ND blocks one exact density, accurately and usually with the cleanest colour. A variable ND is two polarising layers rotating against each other, so one filter dials through a range of densities. Fixed wins on quality and repeatability; variable wins on speed, which is why most solo vloggers run variable and accept its compromises.
| Fixed ND | Variable ND | |
|---|---|---|
| Density | One exact value, as rated | Any point inside its range |
| Colour accuracy | Usually the most neutral | Varies by density; casts are common |
| Speed in the field | Slow: unthread, pocket, thread the next | Instant: twist the ring between takes |
| Covering a full day | Carry two or three filters | One filter covers most light |
| Known artefacts | Very few beyond a possible mild cast | X-cross, colour cast, infrared contamination |
| Best fit | Controlled, repeatable setups | Run-and-gun solo vlogging |
The pattern many creators land on: a variable ND lives on the main vlogging lens outdoors, and one trusted fixed ND64 comes out for hero shots, where a cast or soft corner would be noticed. A few cinema cameras and premium camcorders skip the question with ND built into the body; if yours has it, use it, since internal ND is fixed-density accuracy with variable-level convenience.
However you mount it, buy the filter for your largest lens thread and use step-up rings on smaller lenses. One oversized filter with cheap rings costs less than a filter per lens, and the oversize pushes edge vignetting out of the frame, which matters on wide vlogging lenses.
The X-cross, colour casts and infrared: variable ND artefacts
A variable ND is two polarising filters facing each other, and its three classic problems follow from that construction: a dark X appears past the usable range, colour drifts green or magenta as density rises, and infrared leaks through the darkened glass and muddies blacks. Fixed filters largely dodge all three.
The X-cross. Polarisation is not even across a wide field of view, so at high densities the frame darkens unevenly and a dark X shows, worst on wide lenses and nearest the filter maximum. Makers print minimum and maximum marks on the ring for a reason: the last stretch of rotation is decoration, not usable range. Treat any advertised range above about 7 stops as optimistic; a 9 or 10 stop claim usually means 6 or 7 honest stops.
Colour casts. Many variable NDs lean green, magenta or brown, and the lean grows with density. A mild, even cast can be corrected with a custom white balance saved per density; a cast that varies across the frame cannot, and that uneven kind is the cheap-filter speciality. Our guide to white balance for video covers setting a custom white balance at the camera, the right place to fix an even cast.
Infrared pollution. ND glass is built to block visible light, and at high densities it blocks visible light far better than infrared, so the sensor receives a growing share of infrared the darker you go. The tell-tale result: black clothing turns muddy brown or magenta, shadows go rusty, skin can look flushed, while the rest of the scene seems fine. Worst in hard sun on dark synthetic fabrics. Post cannot fully remove it, because the contamination is mixed into the image. The real fixes are filters with an infrared-cut layer (often labelled IRND) or moderate densities.
One side effect surprises people: a variable ND is polarisers, so it behaves like one. It can deepen skies unevenly on wide shots, kill reflections you wanted on water and glass, and make some screens shimmer with rainbow banding. It is a tool with a known operating window, and the next section is how you find yours.
Test the filter you already own
Five short tests, done once at home, reveal your filter real limits: its colour cast at each density, whether it softens corners, where the X-cross appears on your widest lens, any vignetting, and whether it leaks infrared. Write the results on the filter case and you never guess mid-shoot again.
- Colour cast check. In steady daylight, film a white or grey surface with no filter, then at minimum, middle and maximum density, exposure matched. If the clips drift green or magenta as density climbs, that drift is your cast. Note the white balance Kelvin your camera picks on auto at each density; the growing gap between readings measures the cast better than your eye does.
- Sharpness check. Film a detailed, flat subject, a brick wall or a page of small print, with and without the filter, then compare centre and corners at full size. Haze across the frame, or corners that soften only with the filter on, mark its ceiling.
- X-cross limit. Fit your widest lens, point at a plain bright sky or blank wall, and rotate the ring slowly while recording. Note the position where the dark cross creeps in. That position, not the printed maximum, is your real top end. Many vloggers mark it with a dot of tape on the barrel.
- Vignetting check. Still on the widest lens, compare corners with and without the filter at your usual densities. Corners that darken only with the filter fitted mean the frame is too thick for that focal length, a common problem at 16mm equivalents and wider.
- Infrared check. In bright sun, film something black and synthetic, a backpack or jacket. If the black turns brown or magenta while other colours stay honest, your filter leaks infrared at that density, and it will do the same to every dark outfit and shadow on a sunny shoot.
Ten minutes with a wall, a sky and a black jacket turns marketing claims into your filter personal spec sheet, and tells you which densities you can trust for faces, the only question that matters on a vlog.
The shooting routine: set exposure in the right order
Set frame rate first, shutter second (double the frame rate), aperture third for the look, ISO at its base value, and the ND filter last to bring the exposure in. In that order, the filter absorbs whatever light is left over and nothing downstream fights it.
Two traps catch vloggers who set up in the wrong order. Auto ISO rides up and down as the light changes, so noise and brightness wander between takes of the same scene; lock the ISO and let the filter compensate instead. Auto shutter is worse: it quietly breaks the 180-degree rule the moment light shifts, trading your motion blur away without telling you. Manual exposure with a locked shutter is the whole game.
Build two habits around the ring itself. Glance at its position before every take: a ring knocked in a bag changes exposure between cuts, and the jump shows in the edit. And expect autofocus and screen judgement to get harder at heavy densities: the view through six stops of glass is dim, eye-tracking can hunt in contrasty sun, and a flip screen at midday is hard to read, so shade it with your hand when judging exposure. Our guide to exposure tools for vloggers shows how zebras and a histogram reveal clipping you cannot see on a sunlit screen.
Fixed-aperture cameras: action cams, pocket cameras and phones
Action cameras, pocket gimbal cameras and phones have no aperture to close. On those devices the ND filter is not an accessory for a look; it is the only exposure control left once the frame rate is chosen, which is why ND sets for them sell in packs of three or four densities.
The physics is the same as on a mirrorless camera, only starker. Fix the frame rate at 24 or 30fps and the natural shutter is 1/50 or 1/60. In midday sun the fixed aperture admits far more light than that shutter can use, so without ND the camera races the shutter to 1/1000 or beyond and walking footage turns to jitter. A mid-density filter of 4 to 6 stops brings the shutter back where it belongs. Indoors the filter comes straight off, since these small sensors need every photon going, a point our low-light vlogging tips cover from the other side of the day.
Magnetic and clip-on mounts suit these cameras better than threads, because you swap densities as the light changes. Treat the sets as fixed filters in spirit: each piece is one honest density, colour is usually cleaner than a cheap variable, and the swap costs seconds.
ND filter questions, answered
Short answers to the ND questions vloggers ask most. The thread running through all of them: pick the shutter for the look first, then let the filter do the exposure work.
Do I need an ND filter for vlogging?
If you film outdoors in daylight and want natural motion blur at a wide aperture, yes. Indoors, in shade and near sunset you often need none at all, because the light is already low enough for a 1/50 shutter.
What ND filter do I need for bright sunlight video?
At 24fps, 1/50 shutter and f/2.8, full midday sun calls for about 5 to 6 stops: an ND32 or ND64, or a variable filter working in the middle of its range rather than at its maximum.
What does the 180-degree shutter rule actually mean?
Your shutter speed should be one over twice the frame rate: 1/50 at 24fps, 1/60 at 30fps, 1/120 at 60fps. That ratio gives motion the blur your eye expects, which is why footage shot to the rule reads as cinematic.
ND8 or ND64 for video?
They do different jobs. ND8 is 3 stops, right for shade, overcast days and bright window light. ND64 is 6 stops, the full-sun filter. If you film at midday with a fast lens, ND64 is the one that gets used.
Why does my variable ND show a dark X?
Cross polarisation: past its usable range, the two polarising layers darken the frame unevenly and a cross appears, first on wide lenses. Back the ring off from the maximum mark and the pattern clears.
Can I just use a faster shutter speed instead of an ND filter?
You can, and the exposure will be correct, but motion turns choppy because every frame is frozen sharp. It works for static shots and deliberate high-energy looks. For walking footage, the filter keeps movement smooth.
Does an ND filter affect autofocus?
Light densities barely. Heavy densities darken the image the autofocus system sees, so eye-tracking can slow or hunt, especially in contrasty light. At high densities, grab focus as you set the shot, then record.
Can I stack ND filters?
Yes, and the stops add: an ND8 over an ND64 gives 9 stops. Each added layer raises the risk of vignetting and flare, worst on wide lenses. A fixed filter under a variable dialled low is the smarter stack, keeping the variable out of its artefact zone.
Can I leave a variable ND on indoors?
You can, but it steals light you need. The camera repays the loss with higher ISO and the footage gets noisy. Take it off indoors; five seconds, and your shadows will thank you.
Why do blacks look brown or purple with my ND filter?
Infrared pollution. The filter blocks visible light more strongly than infrared, so at high densities the sensor drinks in infrared and dark fabrics shift brown or magenta. An infrared-cut filter is the fix; editing cannot fully undo it.
Keep exploring
The filter is one control in a chain. These guides cover the settings behind it and the ends of the shooting day where ND stops helping.