K&F 40.5MM Nano-X Variable ND Filter, ND8-ND128

Nano-X — variable ND filter 40.5 mm, changes the amount of light steplessly as you turn it.

• Screws onto a lens with a 40.5 mm thread.
• 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 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 glass has parallel faces and the ring has end stops — the filter cannot be turned into the position where cheap variable NDs produce the dark cross across the frame.