The result of these measurements was 30 true color pictures that were subsequently post processed using software written in Matlab7R14. The software loads the set of 10 pictures acquired for each illuminating color and allows to select,by drag an click operations, regions of interest (ROIs, indicated by white frames areas in Fig. 1c) corresponding to each strip. For each ROI the program calculates the average value along all the vertical pixels of the ROI and repeats the procedure for the10-recorded images.