The Heliopan Vario neutral density filter is adjustable from 1 to 6.6 stops of ND (0.3 to 2.0 density) by simply rotating the calibrated rim of the filter. The Heliopan Vario ND filter is totally neutral in color, it is mounted in a black anodized brass ring that is numerically calibrated for ease in repeating a desired density. The cali- bration scale has an index for added convenience and the adjustable range is hard stopped at each end to save time in set-up and use. The Heliopan Variable ND filter is very thin (8.7mm from the front edge to the front of the lens) to allow it to work on lenses as wide as 16mm without color shifts, vignetting or artifacts common in other variable ND filters.