A low reflectivity coating (40, 80/82) is provided on a substrate (22). The coating includes a layer of substantially vertically aligned carbon nanotubes (40) on an exposed surface (21) of the substrate. Provided on and extending partially within the carbon nanotube layer (40) is a hydrophobic coating (80, 82), in the preferred embodiment of or containing fluorocarbon. The hydrophobic coating (80, 82) prevents any settling or ingress of water particles onto or into the carbon nanotube layer (40) and as a result increases the stability of the carbon nanotube layer during use (40) while improving the low reflectivity of the film.