Rodenstock 604990 49mm Slim Vario Neutral Density Aluminum Mount Multi-Coated Filter Continuously adjustable from 1.5 to 5 full stops (filter factor of 2.8x to 32X) Uses hardened glass with a scratch-resistant coating High-quality optical glass and perfectly plan parallel surfaces with extremely smooth polishing, equal to the best lenses, ensures no loss of sharpness with maximum contrast The extremely thin, but very strong black anodized aluminum mount allows photos free of igniting with most wide-angle lenses and still has a front thread for a lens hood or a lens cap Without cruciform shading, and without a blue-violet color shift