Figures a, yellow lines b, c of FIG three are X, Y, Z tristimulus values of a stepped FIG., The red line is a smoothed value of its difference in level of FIG.
The yellow lines of a, b and c in the figure are the first-order difference of X, Y and Z stimuli, and the red line is the first-order difference of its smooth value.
The yellow lines of a, B and C are the first-order difference graphs of X, y and Z stimulus values respectively, and the red lines are the first-order difference graphs of their smooth values.