I use the term edge to refer to the quality of the transition between shapes of different tonal values. Edges exist on a spectrum from hard to soft to lost edges.

• A hard edge represents a sudden, sharp transition from one tonal value to another. Hard edges tend to draw attention and can be used to create focus or emphasize important elements in a composition. In shading, a hard edge communicates a sudden change of surfacedirection.

• A soft edge shows a more gradual transition between tonal values. You can use soft edges to create a sense of atmosphere and depth in your artwork. In shading, a soft edge communicates a curved surface.

• A lost edge occurs when the transition between tonal values is so subtle that it becomes nearly imperceptible. Lost edges can help integrate forms with their surroundings and create a sense of unity in a composition. In shading, you can find lost edges or subtle gradations in light halftones, reflected light, and ambient occlusion.

The strategic use of different edge qualities is a powerful tool for directing the viewer's attention, creating depth, and communicating form through shading.