Amazon.com : Heliopan 52mm Variable Gray Neutral Density Filter (705290) with Specialty Schott Glass in Floating Brass Ring : Camera Lens Neutral Density Filters : Electronics
Amazon.com : Polaroid Optics 40.5mm Multi-Coated Neutral Density Fader Filter – Variable Range ND2-ND2000– Superior Optical Quality – Compatible w/ All Popular Camera Lens Models : Camera Lens Neutral Density Filters : Electronics