Dorr 82mm Variable Neutral Density 500 DHG Filter. There are some situations in which a photographer desires a longer exposure time, e.g. to create pictures of the sea or flowing water. Unfortunately, the aperture settings can come to its limit in these situations. A variable neutral density filter shades the image even and colour neutrally. By turning the filter, the shade intensity is infinitely variable. Exposure time can be expanded variably.

Exposure time can be expanded from 2.5x to 500x, translating to 1.3 to 9 aperture F-stops.