In preparation for an illustration that I am working on I re-visited the value scale and basic shading. Below is the sketch that I just finished in my pad. After finishing the sketch I did 2 small quick sketches of a sphere to see how I have been approaching this in the past.
Lo and behold, I realized that I have been oversimplifying my shading into 3 main values – spotlight, highlight, and core shadow. *slaps forehead!* This is so wrong haha. This sketch reminded me the that there are no edges in the gradations between values. It is a seamless meld. It is good to re-visit the basics.