Fig. 7
From: Smartphone citizen science: can a conservation hypothesis be tested using non specialist technology?
Measurement of Y 1900-1922 with the iphone6S and X-rite I1 Pro. iPhone6S (White triangles) and X-Rite I1 Pro (Black diamonds) values of the yellowing parameter Y plotted as a function of journal date of issue 1900–1922. The values from the smart phone were found to systematically report a higher value and a global correction values of 0.94 was found to optimally give an overlay of the values on to those of the gold standard. Both detection methods show the stepwise increase in Y in 1912 however the assertion that the Y value was higher for wartime journals specifically is not proven