Comparison of the average intensity contrast of bright fibrils in Ca II K versus Hα (top) and Ca II 8542 Å (bottom); the orange-red filled circles show the fibrils which are bright in both Ca II K and the other line. The grey circles show the ones that are only bright in Ca II K. The distribution of the average intensity difference of the fibrils and their backgrounds are shown in the side-histograms. The Pearson correlation coefficient r is annotated on each panel. The dashed lines show the line y = x.