Reflection from a glossy surface. Many real surfaces are not matt but reflect light, i.e. are glossy; the surfaces of billiard balls, apples, and china are glossy while mirrors are an extreme case, being perfect specular reflectors. If the surface is not a perfect mirror, the reflected light will occur in a cone centred around the perfect reflection direction. The amount of light reflected will be some fraction of the incident light. The result is a highlight that has the colour of the light source rather than of the object. An empirical formula suggested by Bui-Tuong Phong in 1975 is often used in computer graphics to define specular reflection. Compare diffuse reflection.