Transmission, Optical Density and Contrast Ratio
Convert between percentage transmission, optical density, ideal contrast ratio and the percentage of light blocked. Enter a value in any field or select a standard OD preset.
Calculation basis: Contrast ratio assumes a clear reference area transmitting 100% of the incident light. Optical density is wavelength-dependent.
Optical density presets
1
Enter or convert a value
All fields update automaticallyEnter a valid value: transmission must be above 0% and no more than 100%; OD must be 0 or higher; contrast must be at least 1:1.
2
Transmission visual
Logarithmic illustrationIncident light100%
→
PatternOD 4
→
Transmitted0.01%
OD 0OD 6
The illustration uses a logarithmic scale so very low transmission values remain visible.
Transmission0.01%
Optical densityOD 4
Ideal contrast10,000:1
Light blocked99.99%
Transmission
%T = 100 × 10−ODOptical density
OD = −log10(T)Contrast
CR = 10ODProduction guidance
Quoted optical density must be related to an operating wavelength or wavelength range. Substrate reflection and absorption mean that real clear-area transmission may be below 100%, so measured system contrast can differ from the ideal calculated value.
Contact us to confirm the required coating and operating wavelength.