K&F 49MM NANO-X-Magnetic Variable ND8-128 filter

Nano-X Magnetic — variable ND filter 49 mm, changes the amount of light steplessly as you turn it.

• 28 anti-reflective layers
• Magnetic mount — on and off in a second
• The surface repels water and grease and resists scratches

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 goes on magnetically — a magnetic adapter ring screws onto the lens and the filter holds itself on. A swap takes a second and nothing has to be screwed.

The surface repels water and grease, so drops run off and fingerprints wipe away without smears; the coating also stands up to cleaning in the field.

The range is marked on the ring in ND8, ND16, ND32, ND64 and ND128 steps, so it can be set blind. The ring has end stops — the filter cannot be turned into the position where cheap variable NDs produce the dark cross across the frame.