Extend exposure times for creative blur effects that take the viewer beyond the limitations of human perception
NEUTRAL density filters, or NDs, are filters that reduce the amount of light entering the lens allowing you to shoot with slower shutter speeds or wider apertures than you could without. This is ideal if you would like to blur movement, such as clouds or water, in the scene or to shoot with a wider aperture for a shallow depth-of-field.
As the name suggests NDs are neutral, so in the majority of cases they won’t add a colour cast to images. Quality plays a role, so cheaper non-branded NDs may produce colour casts. Standard NDs are available in light-reducing densities of 1, 2, 3 and 4 stops. Extreme NDs are available in 6, 10 and 15 stops, but these will typically alter colour in images which will need to be corrected in post-processing.
Shooting with ND filters that are up to 4 stops in density requires no change in technique – simply attach them to the lens and shoot as normal. With a DSLR the viewfinder will look darker than usual, so you may find that using the LCD screen makes composing easier. With mirrorless cameras, however, you’ll be able to see the image in the electronic viewfinder as clearly as normal.
Things begin to change when you’re shooting with a 6-, 10- or 15-stop ND filter. Since these filters appear opaque to the human eye because of how much light they block, when you attach them to your lens you can’t see an image through the viewfinder or on the LCD with some cameras. With others you can, and in most cases you can shoot normally, but if your camera can’t ‘see’ through these extreme NDs, my guide here will help. Even if you do have a camera that can see through these filters, the guide shows you how to obtain a perfect exposure every time.
ND filters are a great way to blur movement for creative effect