Value

Relates to the lightness or darkness of a color or shade. Think about highlights and shadows.

 

Spheres are made of two shapes, a crescent and an oval.

Depending on the angle of the light hitting it, the sphere is a combination of light crescent (its lit side) and dark oval, or dark crescent (its shadow side) and light oval.

Work on creating subtle transitions.
Your shading strokes should work with the contour edges of the form - round or curver them to follow the shape or your form will appear to be flat.



The Joy of Drawing by Bill Martin, Watson-Guptill Publications, New York,1993. Page 34.