drone

ND Filters for Drone Video, Which Strength to Use and Why Your Footage Needs Them

Most drones have a fixed aperture, and that’s why your daylight drone footage looks jittery. A Mini or an Air shoots at f/1.8 or f/2.8 all the time, so on a sunny day the only way the camera can avoid overexposing is a very fast shutter, 1/2000 or faster. Every frame comes out frozen and sharp, and motion stutters when you play it back.

An ND filter fixes that. It’s sunglasses for the lens. It cuts the light so the camera can use a slower shutter, and the motion blur between frames looks natural again.

The 180-degree rule

Film cameras gave us a simple rule. Set the shutter to about double the frame rate:

  • 24 or 25fps: 1/50
  • 30fps: 1/60
  • 60fps: 1/120
  • 120fps for slow motion: about 1/240

You don’t need to hit it exactly. Anywhere close looks right. What looks wrong is 1/2000 on a pan over a coastline.

Set the shutter manually, set ISO to the lowest value, then pick the ND that gets your exposure right. On the Air 3S, D-Log M goes down to ISO 100.

Which strength

There’s no single chart that works everywhere, but this is the usual starting point at 25 or 30fps:

  • Overcast: ND8
  • Partly sunny: ND16
  • Bright sun: ND32
  • Harsh midday sun, snow or water: ND64

Shooting at 60fps or 120fps for slow motion needs a faster shutter, so drop one step. If ND64 on a bright beach still overexposes, the light is stronger than the filter, and a faster shutter is the lesser evil.

Buy a set of four instead of guessing. DJI sells its own ND8, ND16, ND32 and ND64 sets for most models, and Freewell, PolarPro and K&F Concept make sets for the DJI Mini 4 Pro, the DJI Mini 5 Pro and the DJI Air 3S. Buy filters made for your exact model. They clip onto a tiny gimbal, and the wrong weight can trip a gimbal error.

ND/PL and variable ND

ND/PL filters add a polarizer. That cuts glare on water and glass and deepens a blue sky. The catch is that a polarizer’s effect changes with the angle to the sun, and a drone turns constantly, so a sky can shift from dark to pale during one orbit. Use them for straight lines, not circles.

Variable NDs give you a range on one filter, such as ND2 to ND32. They’re handy on the ground. On a drone you can’t turn the ring in the air, so you set it before takeoff and land to change it, and the strongest settings can show a dark X across the frame. Fixed filters are simpler.

Drones with a real aperture

The DJI Mavic 4 Pro main camera has a variable aperture from f/2.0 to f/11. Stopping down gives you about five stops of control, so you need ND less often. Its two tele cameras are fixed at f/2.8 though, so if you switch lenses mid-flight you’re back to needing a filter. Most Mavic shooters still carry a set.

One more thing. Photos don’t need ND. If you’re shooting stills only, take the filter off and let the shutter be fast.

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