A Neutral Density, or ND for short, is a filter that blocks light entering through the lens and has many uses, namely lengthening the shutter speed for stills photos, or controlling the light when recording video where you can’t control the shutter speed quite so easily.
These Neutral Density filters are so-called because they should have a ‘neutral’ effect on your images and not affect the colors or temperature of your photos. Variable ND filters, or VNDs for short, work in a slightly different way but allow the light to be reduced and the front part of the filter can be turned to allow or restrict light into the lens. VNDs however aren’t semi-transparent pieces of glass, they’re usually two polarizing filters sandwiched together which when turned against one another, they can restrict the flow of light to your desired amount.
