Properties that depend only on the water and other substances that are dissolved or suspended in it, as distinguished from Apparent Optical Properties (AOPs).
The two fundamental IOPs are absorption (a) and the Volume Scattering Function (ß). Others commonly derived from these include the total scattering coefficient (b), backscattering coefficient (bb), and beam attenuation coefficient (c = a + b).
Fluorescence may be considered an IOP although it is usually treated separately from the fundamental properties mentioned above.
Instruments for IOP measurement provide their own carefully controlled illumination and are designed to reject the effects of ambient light. In contrast, AOPs are typically derived from measurements of ambient light.