Reflected Light : Research : Optical Characterisation of Materials : Optical Radiation & Photonics : Science + Technology : National Physical Laboratory

Reflected Light

These visual parameters are usually spectral quantities weighted by the response of the human eye, and single value scales.

	Total reflectance factor - the ratio of the radiant or luminous flux, reflected at all angle within the hemisphere bounded by the plane of the specimen, to the flux reflected from the perfect reflecting diffuser similarly illuminated or viewed.
	Regular (Specular) reflectance - reflection without diffusion, in accordance with the laws of optical reflection, as in a mirror.
	Diffuse reflectance - the ratio of the reflected flux to the incident flux, where the reflection is at all angles within the hemisphere bounded by the plane of measurement except in the direction of the specular reflection (mirror) angle.
	Distinctness-of-image gloss - aspect of gloss characterised by the sharpness of images of objects produced by reflection at a surface.
	Gloss - angular selectivity of reflectance, involving surface reflected light, responsible for the degree to which reflected highlights or images of objects may be seen as superimposed on a surface.
	Haze (reflected) - Light scattering at the glossy surface of a specimen responsible for the apparent reduction in contrast of objects viewed by reflection at the surface; the percentage of reflected light scattered by a specimen having a glossy surface so that its direction deviates more than a specified angle from the direction of the specular reflection; a cloudy appearance attributable to light scattering.
	Orange peel - the appearance of irregularity of a surface resembling the skin of an orange.
	Retroreflection - reflection in which the reflected rays are preferentially returned in directions close to the opposite of the direction of the incident rays, this property being maintained over wide variations of the direction of the incident rays. Classic examples of retroreflectors are the 'cat's eye' in the middle of the road, and safety wear and vehicle licence plates.
	Radiance factor - ratio of the radiance from a point on the specimen, in a given direction, to that from the perfect reflecting, or transmitting, diffuser similarly illuminated or viewed.
	Sheen - the specular gloss at a large angle of incidence (usually 85°) for an otherwise matt specimen.
	Specular gloss - ratio of flux reflected in specular direction to incident flux for a specified angle of incidence and source and detector angular apertures.