Reflektanzvert

Reflektanzvert is a term used in optics and materials science to denote a specific scalar quantity describing the reflectance characteristics of a surface at a defined angular configuration. The name derives from the German "Reflektanz" (reflectance) and a suffix indicating a vertex or defining point in an angular distribution.

It is described as the peak or representative value of reflectance at chosen wavelengths and incident/viewing geometry, often used to characterize anisotropic or specular-dominated surfaces. In practice, the Reflektanzvert may refer to either the angular position (the vertex angle) of maximum BRDF value or to a normalized reflectance measure at that vertex.

Measurements are obtained with angle-resolved reflectometry, using a goniometer or rotating-stage spectrometer to sample incident and observation angles, across wavelengths. The value is computed from measured BRDF or reflectance spectra, sometimes normalized by reference materials. It may be reported as a function of wavelength and material orientation.

It is used in material characterization, calibration of optical sensors, and graphics rendering models that require compact reflectance descriptors. Because it depends on geometry and wavelength, the Reflektanzvert is not universal across conditions and should be specified with measurement setup.

Origin and exact usage vary by literature; some sources treat it as a formal parameter, others as a descriptive label. The term is not standardized in major optical standards, and alternatives such as "reflectance peak" or BRDF vertex are common.