K&F Concept Nano-X variable ND filter ND8–ND128 49 mm

Nano-X variable ND filter ND8–ND128 49 mm, changes the amount of light steplessly as you turn it. It is a favourite for filming on bright days, as it lets you keep a cinematic shutter and a wide aperture without blown highlights or swapping filters between takes.

• 28 anti-reflective layers, reflectance 0.2 %
• Screws onto a lens with a 49 mm thread.
• The surface repels water and grease and resists scratches

Anti-reflective layers

The glass carries 28 anti-reflective layers and reflects only 0.2 % of the light, so no ghosting or veiling appears against the light.

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.