S

Saturation

Saunderson correction
The Saunderson correction takes into account the light that undergoes Fresnel reflection at the air/coating interface. There are two terms, one for directional beams and one for diffuse beams. The directional term describes the reflecton of the light incident on the air/coating interface from the external or air side. The diffuse term describes the reflection of the diffuse light, assumed by Kubelka and Munk, incident on the air coating interface from the internal or coating side. The two terms are given the symbols k₁ and k₂ respectively. The measured reflectance is the product of the Kubelka-Munk reflectance times the Saunderson correction as given in the following equation:



where k₁ is related to the refrative index of the medium as follows:



(k₁ is often given a value of 0.04). The index of refraction, and with it the k₁ value is found to depend to some extent on the pigment volume concentration and is spectrally not completely independent. The above Saunderson correction equation is true for measurements made with the regular (specular) reflectance component included in the measurement. A different form of the Saunderson correction must be used if measurement are made with the specular excluded. That equation is:



One may be tempted to use the specular included equation with the k₁ = 0 as the defining equation for specular excluded but this will not give accurate results. While the measurement system 'excludes' the specular component at some angles or set of angles in the system, the specular component is still present and active in the coating.

Scattering

Scofield colour difference formula

Scotopic vision

SDC

The Society of Dyers and Colourists. Based at Bradford, UK.

Shade

Shade sorting (555)

Sheen

Simon-Goodwin colour difference charts

Simultaneous contrast

Source

Spectral distribution function

Spectrophotometry

Spectrum
The arrangement of colours in order of wavelength.(Red, Orange, Yellow, Green, Blue, Indigo, Violet).

Spectrum locusT
he locus of points on a chromatisity diagram representing monochromatic lights throughout the range of visible wavelengths.

Specular angle
The angle of reflection equal and opposite to the angle of incidence.

Specular component (gloss)
The gloss component of a spectrophotometer measurement which is at the angle equal and opposite to the angle of incidence.

Spex
A abreviation for 'specular (component) excluded'.

Spin, Spinc
An abreviation for 'specular (component) included'.

Standard observer
An ideal observer having visual response described by the CIE tristimulus functions.

Stiles line element

Stokes' law of fluorescence

Strength

Subtractive colour mixing