Illuminance-proxy high dynamic range imaging: a simple method to measure surface reflectance

A technique to measure arbitrarily complex patterns of diffuse surface reflectance under real-world illumination conditions is presented. The technique is founded on high dynamic range (HDR) imaging whereby the luminance values in an HDR image are used to derive average and/or per-pixel values of surface reflectance. Two variants of the method are described and the results from both are compared with analytical solutions. Whilst the technique has general application for the measurement of reflectance, the authors make the case that there is a pressing need to survey occupied building spaces since the notional/typical reflectance values commonly employed in simulation for compliance testing may be quite different from those found in real buildings.