Evaluation of a low-cost method of HDR photography for Daylight Assessment

Thounaojam, A Vaidya, P Mundhe, P Maskarenj, Marshal [UCL]

Evaluation of the daylight performance of buildings can be done with luminance or illuminance measurements. While illuminance has been used in the past for sufficiency of light, luminance-based metrics show the best fit to occupant responses in visual comfort surveys. Luminance measurements are now possible with High Dynamic Range (HDR) techniques that offer a higher spatial resolution at a large field of view. This research evaluates the HDR image acquisition method using smartphone cameras and the calibration of the HDR images using lux meters. Smartphone cameras have been evaluated for their ability to record luminance values in a range of brightness conditions. The error between the low-cost HDR approach and the conventional approach of HDR imaging is determined and a method for correction factors is proposed. A visual comfort survey of a daylit workshop building is done to evaluate the feasibility and accuracy of the low-cost HDR approach