Fig. 5

A scatter plot of the xy values obtained from the journal collection. An indication that the vector length of the xy coordinate is sufficient to describe the yellowing. Blue numbers around the edge of the gamut indicate wavelengths of light. The data points obtained from the X-Rite I1 Pro are shown as blue squares and cover a range of the yellow gamut in the CIE xy 1931 colour range they are laid over. Xy values from the iPhone 6s are shown as green circles. The vector product of xy is used to determine level of yellowing