Photobiologically Active Radiation, or PBAR, designates the range of wavelengths of light shown to effect plant growth, from 280 to 800 nanometers (nm). This range extends from non-visible ultraviolet (UV) light, through the entire visible / PAR light range and into the non-visible infrared (IR).

Photosynthetic Active Radiation (PAR) designates the visible light range of 400-700nm, and was originally thought to be the only light plants used for photosynthesis. However, scientists discovered in the last century that infrared light from 700-750nm enhances photosynthesis, known as the Emerson Effect. They also discovered that ultraviolet light contributes to photosynthesis while also offering many other benefits. This makes PAR an outdated metric for the range of wavelengths that are useful for growing plants.

PBAR includes the entire PAR range as well as being a much better range to evaluate how light will effect plant growth.

Photobiological Photon Flux (PBF) is the metric used to measure the total number of photons in the PBAR range, and Photobiological Photon Flux Density (PBFD) is the metric for measuring intensity of light in the PBAR range.