Calculating luminous flux radiated to a camera lens via high dynamic range photogrammetry

Abstract

A camera-aided method of using high dynamic range photogrammetry was developed to calculate luminous flux radiated to the camera lens from an environment or its subareas, with per-pixel contributions from visible light-emitting sources, objects, and reflective surfaces. A series of equations were derived to calculate the luminous flux with valid sub-divisibility and additivity. A pilot study was first conducted, followed by a laboratory experiment using an integrating sphere to improve and validate this high dynamic range imaging method with a measurement error of 5.6%. This method was then tested in a real office space to estimate ‘visible’ luminous flux arriving at the camera lens simulating a typical view of 30 office users under four different test scenarios (fluorescent vs. LED lighting, with vs. without access to lighting controls). The luminous flux retrieved from each of a total of 120 high dynamic range images was checked with the illuminance measured at the camera lens. This camera-aided method for remote measurement of luminous flux was proven valid and useful for lighting practice and research. Further investigations on this method are necessary to overcome several limitations and issues of the present study.