Still not quite convinced by the calculated values for the bevelled cube I did the only sensible thing I could think of and made some to test. (Very simple, just bits of wood cut to shape with a bandsaw and painted with acrylics.)
Then painted a picture of them under ordinary studio light taking care to match the values I was seeing:
It doesn’t work with Apollo’s values because I am seeing the effect of two light sources (the overhead light which lights my easel plus the one set up for the subject.) My mistake. Tried again with a shadow box to exclude the top light.
I actually tried many lights and setups but could not recreate Dorian’s values for light and shade. The darkest I could get the white in shadow was V7 – a long way short of his V4.
Also the value for the light side of the black cube measured at V4. I found it impossible to replicate the rule-of-thumb taught everywhere that “a black cube in the light is the same value as a white cube in shadow”.
This exercise for me has highlighted the value (couldn’t resist the pun) of actually recreating examples rather than merely accepting something read in a book. Any book.