Neutral Density Filters

Neutral Density Filters are gray filters which are designed to evenly block out a percentage of all visible light.

Since adding a Neutral Density filter reduces the amount of light we will need to adjust the Shutter Speed and/or Aperture.

One reason to use a Neutral Density Filter is to increase the aperture opening of your lens. This is done to achieve a shallower depth of field, separating your subject from your background. Keeping your subject in sharp focus while blurring the background.

More commonly though a Neutral Density Filter is to slow the shutter speed to capture a motion blur.

Since there is less light entering the lens, you can reduce the shutter speed without needing to change the aperture. Using a Neutral Density Filter can let you shoot at a very slow shutter speed even if it is bright out.

When taking a photograph of a waterfall it is common for a photographer to use a neutral density filter to slow down the shutter speed. That way instead of freezing the action of the waves and seeing individual water drops, the water is softer and more flowing.

There are three levels of Neutral Density Filters which block out different percentages of light.

ND 2 or ND 0.3 - Blocks 1 f-stop

ND 4 or ND 0.6 - Blocks 2 f-stops

ND 8 or ND 0.9 - Blocks 3 f-stops

Neutral density filters can be combined together for a greater effect. For example you can combine an ND 2 and ND 8 to create a ND 10 that blocks 4 f-stops.

If you are looking to combine ND filters you should use a drop style filter like the ones by Lee or Cokin. Stacking traditional circular filters will result in vignetting around the edges of your photos, especially on wide angle lenses.