Hereís something else interesting hiding in the diagram. Remember in the speed/meter relationship post when I said that the average scene highlight falls 3 stops above the metered exposure and the average shadow falls 4 1/3 stops below, but in camera with the effects of flare, they balance out making the metered exposure the mean?
Kodak tone reproduction graphic a.jpg
The four red arrows are the same length. They are based on the distance between the highlight point and three stops down (which can be considered the metered exposure point) in the Subject representation. With the Optical Image, this relationship hasnít changed, but the distance between the metered exposure point and the shadow exposure is reduced almost to the same three stop difference. I have to admit it's not perfect in this example because the amount of flare they use is slightly lower than average. I believe they had to "fudge" some in order to make the rounded 7 stop range (instead of 7 1/3 stops) fit into the 1.05 negative density range.