Local Value vs. Illumination: Separating Color from Light
The most common mistake in rendering is confusing illumination for the object’s inherent shade.
value-study
The 3-Value Hierarchy: Establishing Instant Readability
Your brain needs to see clear, distinct groups of tone to understand what is happening in the scene.
Value Keying: Setting the Emotional Tone with Math
Using the full scale from pure black to pure white in every drawing is like shouting at the top of your lungs for the entire duration of a conversation.