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 |
