Neutral Density (ND) filters are designed to reduce transmission evenly across a portion of a specific spectrum. It is just the values of “VD” and “ND”. Then what do they. An ND filter is simply a darkened piece of glass that you can place in front of the lens to limit the amount of light that can pass through. 9, or factors such as ND1000 (about 10 stops). Variable designs use two polarizers to tune strength, while graduated types shift from clear to dark for horizons. Expect practical tips on converting a numbered rating into shutter and. What does ND stand for? Sort results: alphabetical | rank ? 82 definitions of ND.