Experimental setup of photometric imaging system used in this study. Panel a: layout of the whole imaging system. The upside-down beaker on the sample plate is to protect the samples and is removed during measurement. Panel b: enlarged view of the light source showing how the filters were installed during measurement. Panel c: details of the cage system that were used to fix the fiber and to adjust the size of the light spot. Panel d: transmission spectra of the four filters used in this study.