albedon

Albedon is a proposed radiometric concept related to surface reflectivity, intended to capture how a surface reflects light when the spectral distribution of the illumination is taken into account. It is distinct from standard albedo in that albedon explicitly weights reflectance by a specified illumination spectrum, making it a spectrum-dependent measure rather than a single broad fraction.

Mathematically, for a surface with spectral reflectance R(λ) and an incident spectral power distribution S(λ), albedon can be defined as A_d = ∫ R(λ) S(λ) dλ / ∫ S(λ) dλ over a defined wavelength range. The result is a dimensionless quantity between 0 and 1. The choice of S(λ) determines the weighting, with common examples including the solar spectrum (AM1.5G) or a given artificial-light spectrum.

Distinction from albedo lies in the explicit inclusion of the illumination spectrum. While albedo describes reflectivity averaged over an unspecified or broad spectrum, albedon conveys how reflectivity behaves under a particular lighting condition. Consequently, albedon is primarily a modeling or analysis convention rather than a universally adopted standard physical quantity.

Applications of the concept include climate and energy balance studies, architectural and lighting design, and computer graphics, where accurate radiative exchange depends on the spectrum of either natural or artificial illumination. It facilitates comparisons of materials or surfaces under different light sources and can inform assessments of radiative forcing or energy efficiency.

Measurement of albedon relies on spectrally resolved reflectance data and knowledge of the illumination spectrum. Practically, R(λ) is measured with spectroradiometry or integrating-sphere methods, then integrated against the chosen S(λ) to compute A_d. See also albedo, spectral reflectance, radiometry, photometry.