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ND filter density
Convert logarithmic optical density to ideal light transmission and exposure reduction in stops.
Optical density (OD): 0–6
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ND filter density
Optical density (OD): 0.9
- Light transmission (%)
- 12.589254
- Exposure reduction (stops)
- 2.989735
Transmission = 100 × 10^(−D) percent; stops = D / log₁₀(2). Enter dimensionless optical density D from 0 to 6, including fractions. D = 0 transmits 100%; D = 1 transmits 10% and reduces exposure by 3.321928 stops. Exact one-stop density is log₁₀(2), about 0.301030: a nominal OD 0.3 is only approximately one stop. A filter factor such as ND8 is not optical density 8; check the manufacturer’s notation. This ideal scalar conversion does not predict spectral neutrality, infrared leakage, polarisation, variable-ND artefacts, angle dependence or actual camera exposure. Use measured transmission or manufacturer data for the relevant wavelength band. Display uses six decimals; calculations retain precision.
Methodology
How it works
Transmission = 100 × 10^(−D) percent; stops = D / log₁₀(2). Enter dimensionless optical density D from 0 to 6, including fractions. D = 0 transmits 100%; D = 1 transmits 10% and reduces exposure by 3.321928 stops. Exact one-stop density is log₁₀(2), about 0.301030: a nominal OD 0.3 is only approximately one stop. A filter factor such as ND8 is not optical density 8; check the manufacturer’s notation. This ideal scalar conversion does not predict spectral neutrality, infrared leakage, polarisation, variable-ND artefacts, angle dependence or actual camera exposure. Use measured transmission or manufacturer data for the relevant wavelength band. Display uses six decimals; calculations retain precision.
Method and assumptions documented by Techrider.live
2026-10-27
Frequently asked questions
Does OD 0.9 mean exactly three stops?
No. OD 0.9 gives 12.589254% transmission and about 2.989735 stops. Exactly three stops corresponds to OD 0.903090 and 12.5% transmission. Nominal filter markings may be rounded.