is the logarithm to the base ten of the reciprocal of the transmittance: OD = log10(Ei/Et), where OD = optical density, Ei = incident beam irradiance (W/cm2) worst case exposure, and Et = transmitted beam irradiance (MPE limit in W/cm2).

The ability of a material to absorb light. The darker the material, the higher the density. Density is usually expressed on a logarithmic scale of Optical Density (O.D.) units.

The logarithm to base 10 of the inverse of the transmittance.

nbspLightness or darkness measured with a densitometer.

A measurement of the transmission of light through the cross-hatch area (Densichron).

the degree to which a refractive medium retards transmitted rays of light.

(OD): Units measuring transmission usually in blocking regions. Conversion: -log10(T) = OD. Example: 1% transmission is 0.1 absolute, so -log10 (0.01) = OD 2.0.

Light-absorbing capacity of an image area.

the intensity of color or the printed image