K&F Universal Phone Filter ND2-400

Nano-K — variable ND filter, changes the amount of light steplessly as you turn it.

• 18 anti-reflective layers

A variable ND replaces a whole set of fixed grey filters — turning the front ring changes how much light gets through, steplessly. While filming the shutter stays at 1/50 s even as the sun goes behind a cloud and comes back, with no need to stop the take or swap a filter.

The filter screws into the clip, the clip goes onto the phone, and the density is then set by turning the front ring through the full 360°. The same filter has a 52 mm thread, so it will also screw onto a camera lens.