quality:correction, information:highlighting
History

The earliest studies of gloss perception are attributed to Ingersoll who in 1914 examined the effect of gloss on paper. By quantitatively measuring gloss using instrumentation Ingersoll based his research around the theory that light is polarised in specular reflection whereas diffusely reflected light is non-polarized. The Ingersoll "glarimeter" had a specular geometry with incident and viewing angles at 57.5°. Using this configuration gloss was measured using a contrast method which subtracted the specular component from the total reflectance using a polarizing filter.

In the 1930s work by A. H. Pfund, suggested that although specular shininess is the basic (objective) evidence of gloss, actual surface glossy appearance (subjective) relates to the contrast between specular shininess and the diffuse light of the surrounding surface area (now called "contrast gloss" or "luster").

If black and white surfaces of the same shininess are visually compared, the black surface will always appear glossier because of the greater contrast between the specular highlight and the black surroundings as compared to that with white surface and surroundings. Pfund was also the first to suggest that more than one method was needed to analyze gloss correctly.

In 1937 Hunter, as part of his research paper on gloss, described six different visual criteria attributed to apparent gloss. The following diagrams show the relationships between an incident beam of light, I, a specularly reflected beam, S, a diffusely reflected beam, D and a near-specularly reflected beam, B.

Defined as the ratio of the light reflected from a surface at an equal but opposite angle to that incident on the surface.

Defined as the gloss at grazing angles of incidence and viewing

Defined as the ratio of the specularly reflected light to that diffusely reflected normal to the surface;

Defined as a measure of the absence of haze or a milky appearance adjacent to the specularly reflected light: haze is the inverse of absence-of-bloom

Defined as the sharpness of the specularly reflected light

Defined as the uniformity of the surface in terms of visible texture and defects (orange peel, scratches, inclusions etc.)

A surface can therefore appear very shiny if it has a well-defined specular reflectance at the specular angle. The perception of an image reflected in the surface can be degraded by appearing unsharp, or by appearing to be of low contrast. The former is characterised by the measurement of the distinctness-of-image and the latter by the haze or contrast gloss.

In his paper Hunter also noted the importance of three main factors in the measurement of gloss:

For his research he used a glossmeter with a specular angle of 45° as did most of the first photoelectric methods of that type, later studies however by Hunter and Judd in 1939, on a larger number of painted samples, concluded that the 60 degree geometry was the best angle to use so as to provide the closest correlation to a visual observation.