This drawing shows a simple sphere form illuminated from the upper right side of the page. The area where the form picks up the light the most has a HIGHLIGHT, which is a shape that is the lightest value.
The CAST SHADOW shows where light is blocked by part of the object (or something else) and makes the darkest value. The MIDTONE VALUE is a tone that is between the CAST SHADOW and HIGHLIGHTS. Many values are used, on a scale from darkest to lightest, to show the form of an object as it is lit up by a light source. This drawing shows how adding a DARK TONE shows the roundness of the bottom of the sphere, |