Gloss is an optical property, which is based on the interaction of light with physical characteristics of a surface. It is actually the ability of a surface to reflect light into the specular direction. The factors that affects gloss are the refractive index of the material, the angle of incident light and the surface topography. See also list of optical topics. ... A specular highlight on a rendered sphere. ... Surface of the Earth Topography, a term in geography, has come to refer to the lay of the land, or the physiogeographic characteristics of land in terms of elevation, slope, and orientation. ...

Gloss can be said as a view of material appearance. Materials with smooth surfaces appear glossy, while very rough surfaces reflect no specular light and therefore appear matte. Gloss is also expressed as lustre or sheen in certain fields of application. Lustre (American English: luster) is a description of the way light interacts with the surface of a crystal, rock or mineral. ...

Qualitative and Quantitative View of Gloss

Surface gloss is considered to be the amount of incident light that is reflected at the specular reflectance angle of the mean of that surface. So, specular gloss is proportional to the reflectance of the surface. In optics, reflectivity is the reflectance (the ratio of reflected power to incident power, generally expressed in decibels or percentage) at the surface of a material so thick that the reflectance does not change with increasing thickness; , the intrinsic reflectance of the surface, irrespective of other parameters such as the...

The Fresnel formula gives the specular reflectance, R_s, for an unpolarized light of intensity I₀, at angle of incidence i, giving the intensity of specularly reflected beam of intensity I_r, while the refractive index of the surface specimen is m. Augustin Fresnel Augustin-Jean Fresnel (pronounced fray-NELL) (May 10, 1788 – July 14, 1827), was a French physicist who contributed significantly to the establishment of the wave theory of light and optics. ... In physics, intensity is a measure of the time-averaged energy flux. ...

The Fresnel equation is given as follows : Augustin Fresnel Augustin-Jean Fresnel (pronounced fray-NELL) (May 10, 1788 – July 14, 1827), was a French physicist who contributed significantly to the establishment of the wave theory of light and optics. ...

Surface Roughness

Figure1:Specular reflection of light from a rough surface

Surface roughness in micrometer range influences the specular reflectance levels. The diagramme on the right depicts the reflection at an angle i on a rough surface with a characteristic roughness height h. The path difference between rays reflected from the top and bottom of the surface bumps is: Image File history File links Nanorough. ... Image File history File links Nanorough. ...

When the wavelength of the light is λ, the phase difference will be:

If is small, the two beams (see Figure 1) are nearly in phase and therefore the specimen surface can be considered smooth. But when , then beams are not in phase and through interference, cancellation of each other will occur. Low intensity of specularly reflected light means the surface is rough and it scatters the light in other directions. If an arbitrary criterion for smooth surface is , then substitution into the equation above will produce:

This smooth surface condition is known as the Rayleigh criterion.

Gloss Measurement

Specular reflection is measured with a specular glossmeter. Unpolarised white light is concentrated by a condenser lens onto a field aperture, which is located in the focal plane of the source lens. The reflected beam at the surface is later collected by the receptor lens. The intensity of the beam is then measured through a photodetector. The term condenser has the following meanings: In electronics, it is another (old-fashioned) word for capacitor. ... In optics, an aperture is something which restricts the diameter of the light path through one plane in an optical system. ...

The common angles of incidence for gloss measurement are 20°, 60° and 85°. Low gloss surfaces are recommended to be measured with 85° settings.

The typical standards for gloss measurements are ASTM D 2457, DIN EN ISO 2813 and DIN 67530. Standards organizations are bodies, organizations and institutions that produce, and in some cases measure, standards. ... ASTM International is an international voluntary standards organization that develops and produces technical standards for materials, products, systems and services. ... Deutsches Institut für Normung e. ...

References

• Meeten, G.H., "Optical Properties of Polymers," Elsevier Applied Science, London, 1986, pp. 326 - 329. ISBN 0-85334-434-5