What Is a Neutral Density Filter in Photography?

A filter used in front of the lens that absorbs all visible wavelengths and significantly reduces the amount of light that reaches the sensor. Neutral density filters are particularly useful in situations where excess ambient light does not allow you to use the shutter speed and aperture you require to achieve a desired photographic effect. One example would be photographing daytime seascapes where you wish to use a long exposure time to allow blurring of the water to create a sense of dynamic movement.

 

F-Stop Reduction Optical Density Filter Factor % transmittance
0 0 0 100
1 0.3 2 50
2 0.6 4 25
3 0.9 8 12.5
4 1.2 16 6.25
5 1.5 32 3.125
6 1.8 64 1.5625
7 2.1 128 0.78125
8 2.4 256 0.390625
9 2.7 512 0.1953125
10 3.0 1024 (sometimes called ND1000) 0.09765625
11 3.3 2048 0.048828125
12 3.6 4096 0.0244140625
13 3.9 8192 0.01220703125
13 1/3 4.0 10000 0.01
14 4.2 16384 0.006103515625
15 4.5 32768 0.003051757813
16 4.8 65536 0.001525878906
16 2/3 5.0 100000 0.001
17 5.1 131072 0.0007629394531
18 5.4 262144 0.0003814697266
19 5.7 524288 0.0001907348633
20 6 1048576 0.00009536743164