daylightequivalent

Daylightequivalent is an informal metric used to describe the perceived brightness of a light source in terms of daylight. It expresses how strong or visually impactful a lamp is compared with natural daylight under specified viewing conditions, often presented as a lux value at a task plane or as a qualitative descriptor. The term is not standardized, but it is used in some marketing and design contexts to provide an intuitive sense of brightness.

In practice, calculating a daylightequivalent involves comparing the luminance and spectral characteristics of the light source to daylight, taking into account human visual response (photopic vision), color temperature, and color rendering. Vendors may convert luminous flux to a lux figure at a given distance or mounting height, or report a daylight equivalence for a particular working area. In horticultural settings, a related idea sometimes appears as a daylight equivalent for artificial photosynthetically active radiation, though that is more typically expressed in PPFD or DLI rather than lux.

Use of the concept is common in interior design, architectural lighting, and consumer electronics marketing to give a quick sense of brightness relative to daylight. However, daylight itself varies greatly in intensity and spectral composition throughout the day, so daylightequivalent values are approximate. They should be interpreted alongside the product’s spectrum, correlated color temperature, color rendering index, and the lighting geometry of the installation. There is no universally adopted standard for reporting daylightequivalent, which can lead to inconsistent or misleading comparisons if used in isolation.