Glossary of optical radiation terms including both phometric units and radiometric units [2] at the International Light website [3]. We note that while it's clear to those familiar with both Photometry and Radiometry, it is not 100% clear from this Glossary that all measures in the Photometric scales and units pertain to human vision. That is, photometers measure luminous intensity or luminance while radiometers measure radiant power. One has to look a little bit into this Glossary to find the distinction: "Photometer -- A device for measuring luminous intensity or luminance. A photometer employs a photopic filter which has a band pass that is matched to the human eye response. The S.I. units employed are lumens and lux." Whereas: "Radiometer -- A device for measuring the intensity or accumulation of radiant energy. "