Optical Density to Transmission Calculator
OD
Transmission
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%
Attenuation
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dB
Scientific Notation
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How it works?
Optical Density (OD) is a logarithmic unit used to measure the attenuation of light passing through an optical filter or material. It is widely used because it allows filter effects to be stacked additively (e.g., OD 1 + OD 2 = OD 3).
$$ OD = -\log_{10}(T) \quad \text{and} \quad T = 10^{-OD} $$
Optical Density Equation
Where:
- Optical Density (OD): The value representing blocking power. An OD of 1 blocks 90% of light; an OD of 2 blocks 99%.
- Transmission ($T$): The fraction of light that passes through. In the formula above, $T$ is a value between 0 and 1 (e.g., 10% transmission = 0.1).
- Decibels (dB): Another common attenuation unit. The relationship is simple: $1 \text{ OD} = 10 \text{ dB}$.
Example: Laser safety goggles rated at OD 6 will transmit only $10^{-6}$ (one millionth) of the incident power, effectively reducing a 1 Watt beam to 1 microwatt.