K&F Concept Nano-X MCUV UV Filter Ultra-Low Reflection, 40.5 mm

Nano-X — UV filter 40.5 mm, protects the front element and filters ultraviolet light. It is the cheapest insurance for a lens: drops, dust, fingerprints and small knocks land on the filter, while it takes no light and leaves colours unchanged.

• 28 anti-reflective layers, reflectance 0.1 %
• Screws onto a lens with a 40.5 mm thread.
• The surface repels water and grease and resists scratches

An MCUV filter does two jobs at once. It filters out the ultraviolet light that puts a bluish veil over distant and mountain shots, and above all it shields the front element — instead of a scratched lens you replace a filter costing a fraction. It has no other effect on the picture, so it can stay on permanently.

The glass carries 28 anti-reflective layers and reflects only 0.1 % of the light, so no ghosting or veiling appears against the light.

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 glass is tempered to 9H hardness, so it stands up to the sand and grit that would scratch an ordinary filter. That makes it protection for the field — on a motorbike, in the desert or at the beach — rather than a token cover.