When asked in the Check and Log section for Part I, Project 3: Tone and Form, whether I found it difficult to distinguish between light from primary source and secondary reflected light, I realized that I wasn’s sure whether I had understood these concepts. A Google search brought up several sources, of which I have chosen two to summarize the idea:
Graphical illustration 1
source: http://www.learntoart.com/index.php/archives/drawing/how-to-shade/
Graphical illustration 2: Five areas
Specifically, five different light/shade areas can be distinguished on an object which is directly lit, i.e. with light going from a source straight to the object:
A: Highlight: The lightest point or area of the object
B: Halftone: Medium tone area
C: Core shadow: The darkest area of the object
D: Reflected light: This area is in the shadowy areas of the object, but it receives reflected light from another surface and therefore is lighter than the core shadow area
E: Cast shadow: The shadow which is cast from the object onto other surfaces, also a very dark area.
source: http://www.stanprokopenko.com/blog/2009/08/direct-light/