Visual appearance

The visual appearance of objects is given by the way in which they reflect and transmit light. The color of objects is determined by the parts of the spectrum of (incident white) light that are reflected or transmitted without being absorbed. Additional appearance attributes are based on the directional distribution of reflected (BRDF) or transmitted light (BTDF) described by attributes like glossy, shiny versus dull, matte, clear, turbid, distinct, etc. Since "visual appearance" is a general concept that includes also various other visual phenomena, such as color, visual texture, visual perception of shape, size, etc., the specific aspects related to how humans see different spatial distributions of light (absorbed, transmitted and reflected, either regularly or diffusely) have been given the name cesia. It marks a difference (but also a relationship) with color, which could be defined as the sensation arising from different spectral compositions or distributions of light.

Appearance of reflective objects
The appearance of reflecting objects is determined by the way the surface reflects incident light. The reflective properties of the surface can be characterized by a closer look at the (micro)-topography of that surface.

Structures on the surface and the texture of the surface are determined by typical dimensions between some 10 mm and 0.1 mm (the detection limit of the human eye is at ~0.07 mm). Smaller structures and features of the surface cannot be directly detected by the unaided eye, but their effect becomes apparent in objects or images reflected in the surface. Structures at and below 0.1 mm reduce the distinctness of image (DOI), structures in the range of 0.01 mm induce haze and even smaller structures affect the gloss of the surface.

diffusion, scattering''': process by which the spatial distribution of a beam of radiation is changed in many directions when it is deviated by a surface or by a medium, without change of frequency of its monochromatic components.
 * '''Definition

Terminology
Reflective objects


 * Reflectance factor, R
 * Gloss reflectance factor, Rs
 * Gloss (at least six types of gloss may be observed depending upon the character of the surface and the spatial (directional) distribution of the reflected light.)
 * Specular gloss
 * Distinctness of image gloss
 * Sheen
 * Reflection haze, H (for a specified specular angle), the ratio of (light) flux reflected at a specified angle (or angles) from the specular direction to the flux similarly reflected at the specular angle by a specified gloss standard.

Transmissive objects


 * Transmittance, T
 * Haze (turbidity)
 * Clarity