Types of Surface Light Reflection
Diffuse Reflection
From bib. source
Diffuse reflection […] gives objects depth and dimension, […]. As light is reflected from a diffuse surface it is scattered along a very wide axis, and there is only the vaguest sense of what is in fact being reflected […]
Thus, the first type of reflective behavior of a surface is for it to diffuse the light it reflects off itself (Yot 2020, 65). Diffusion means the reflective light is scattered by the pigmentation of the surface enough that any image that could be in it is extremely blurred and mixed at best and at worst is converted into a composite hue from all the colored lights hitting the given surface, with the hue native to the pigment predominating (recall that pigments act like filters on light) (Ibid).
Specular Reflection
The second type of reflective behavior a surface may have is (Ibid):
From bib. source
[ …] called direct reflection, or specular reflection. This is the kind of reflection you get from mirrors, polished metals and water. In this case there is much less diffusion and therefore a much clearer image of what is being reflected.
That is, the images are more detailed, less blurred and more visible with specular reflection or direct reflection (Ibid). The pigment of the given solid doesn’t skew the hues of the parts of the specular reflection as much as it would in the diffuse reflection scenario, although it determines the overall tint layered over the resultant specular image (Ibid).
Volume as Conveyed by Reflection
Given these differences between diffuse and specular reflection, it can be said that a specular reflection from or on a solid provides information about the solid’s environment and space, via the way its geometry distorts the resultant image on its surface, while a diffuse reflection from or on a solid provides information about that solid’s volume (Ibid). In the former case shade defines form while in the latter case image distortion defines form (Ibid). In nature, diffuse reflections are more common than specular reflections (Yot 2020, 66).
Translucency, Transparency and Incandescence
There exists other reflective behavior for surfaces in addition to specular or diffuse reflection, namely (Ibid):
- Translucency / transparency, in which most light simply passes through the surface of a solid, with some occasional divergence and diversion of the light rays, revealing what is behind it. It is the opposite of reflective, but also does not work like most pigment insofar as there is no absorption of any color of light as heat. That is to say, translucency/transparency can be seen as a pigment that neither reflects light of any hue (for the most part) nor absorbs light of any hue as heat.
- Incandescence, in which light is emitted by the surface of a solid.
reflectivity reflected_light blur reflected_light reflectivity specular_reflection direct_reflection metal mirror images light_source bounced_light specular_image translucency incandescent_lighting incandescent_light incandescence pigments form forms spatial_volume optics
bibliography
- “How We Perceive Surfaces.” In Light for Visual Artists: Understanding and Using Light in Art & Design, 2nd ed., by Richard Yot. Laurence King Publishing, 2020.