Variable ND Filter
A filter made of two stacked polarisers whose relative rotation continuously varies the amount of light blocked.
Measured in
stops (EV)
In depth
Its convenience — typically two to eight stops from a single filter — comes with real compromises. Because it is polarising, it darkens skies unevenly on wide lenses, and beyond about six stops most units show a dark cross-shaped band across the frame. Videographers accept these limits for the ability to hold a 180° shutter as light changes.
Examples in practice
A filmmaker rotates a variable ND to hold 1/50 s at f/2 while walking from shade into direct sun.