Neutral Density Filters have four main uses:

• Allowing the use of slow shutter speeds, especially with high-speed films, enabling the capture of motion in subjects such as waterfalls, clouds, or cars.
• Reducing depth of field by allowing wider apertures to be used, which helps separate subjects from their background.
• Reducing the effective ISO in high-speed films (over ISO 400) and allowing their use outdoors in bright conditions.
• Allows cine and video cameras (which have fixed shutter speeds) to film subjects such as snow, sand, or other bright scenes that could cause overexposure.

Neutral Density Factors:

• 2x = ND.3 (exposure adjustment = 1 stop, ISO reduction 1/2)
• 4x = ND.6 (exposure adjustment = 2 stops, ISO reduction 1/4)
• 8x = ND.9 (exposure adjustment = 3 stops, ISO reduction 1/8)