Provides Fixed 3 f-stop Light Reduction, B270 Schott Optical Glass, 20-Layer Nano-Coated. The 39mm Soft Graduated ND8 Lens Filter Plus+ from Urth provides a fixed 3 f-stop light reduction from half your image for balanced exposure and better dynamic range in soft graduated light conditions. By blocking 3 f-stops of light from half the image you can balance your exposure when the foreground is darker than the background - such as shooting landscapes in the mountains. The soft graduation creates a natural blending of light. The Plus+ range features 20-layers of nano-coating providing easier cleaning and better protection against water oil and scratches. These layers also provide a higher maximum light transmission and a more consistent transmission curve for truer light reduction.