The ProMaster Digital HGX Variable Neutral Density Filter variable neutral density filter providing light reduction of about 1.3 to 8.6 stops. The ND3 to ND400 density creates a darkening of the entire image, allowing you to photograph with a wider aperture or slower shutter speed than normally required.ProMaster Digital HGX filters are the most advanced optical filters available today for digital photography featuring: Next Generation Digital Anti-Reflection Multi Coating Specially formulated to minimize internal reflections created by CCD and CMOS sensors in a digital SLR. REPELLAMAX Element Resistant Coating This EXCLUSIVE PROMASTER coating repels moisture, fingerprints, dust, dirt, and grime to ensure the sharpest images possible Hardened Optical Glass Ultra hardened optical glass resists surface scratching and stands up to the most intensive use. Low Profile Anti-Reflective Frame Ultra thin low profile frame helps prevent vignetting on super wide digital format lenses. The satin-like smooth finish helps to minimize reflected light. Black Rimmed Glass The outer rim of the filter glass is treated with a special black-ink.