Flexible calibration method: Photometric and radiometric measurements with compact low-cost multi-channel sensors

Compact multi-spectral sensors present a cost-effective solution for portable light measurement, yet their radiometric accuracy and spectral reconstruction capabilities remain under-characterised compared to laboratory-grade spectroradiometers. This study presents a systematic method for evaluating and calibrating a commercial sensor with a discrete set of spectral channels. The absolute radiometric responsivity was characterized using both laboratory-standard and readily accessible illumination sources, thereby demonstrating that the calibration is independent of the particular light source. Furthermore, the spectral power distribution reconstruction was evaluated under various illumination conditions, correctly estimating radiometric and photometric quantities for visual and non-visual systems. The results also show that increasing the number of spectral channels improves reconstruction accuracy primarily when the channels are well distributed over the spectral range, while additional overlapping bands provide only marginal benefits.