lumels

Lumels are a theoretical metric of luminous energy defined by the International Commission on Illumination in 2023 as a unit equivalent to the radiant flux emitted by a standard light source at a fixed distance under controlled environmental conditions. Unlike the more widely used lumen, which measures luminous flux perceived by the human eye, a lumel incorporates factors such as spectral distribution, temporal stability and photon quality metrics. The term originates from the Latin root "lumen" combined with the suffix "-el" to denote a subunit, and has been adopted in scientific literature to allow precise specification of light source performance in high‑precision optical experiments.

Applications of lumels appear in advanced photonics research, particularly in the calibration of quantum‑efficiency detectors and the characterization of laser diodes for space‑based optical communication. The metric also facilitates comparison of LED products where color temperature variance can bias lumen-based measurements. In engineering contexts, lumel values are employed in the design of illumination systems for semiconductor fabrication, where energy allocation must be tightly controlled for process uniformity.

The acceptance of lumels within the scientific community remains gradual. Researchers have published comparative studies indicating that lumel‑based reporting reduces measurement uncertainty for broadband emitters. Technical standards published by the Optical Society of America in 2025 recommend reporting both lumens and lumels for new photonic devices. Although lumels are not yet part of the SI base units, the proposed metric is expected to become increasingly common in high‑precision photometric surveys and aerospace optics specifications.