Chiaroscuro is the study of light and shadow. One of the keys to shadow is the edges. Form shadows yield soft edges and cast shadows yield sharper edges. Edges, however, are relative. For example, a soft edge next to an even softer edge will appear hard. To clarify the types of edges, we can divide them into the following four categories.
1.Soft Edges: Soft edges are soft due to the curving of a form, such as the edges of a form shadow where there is a gradual change from light to shadow.
2. Firm Edges: Like soft edges, firm edges fall within the category of form shadow; however, firm edges consist of a more abrupt turn from light to shadow than do soft edges. An example of a firm edge would be in the turning from light to shadow on the bridge of the nose. These edges are generally found where there is bone on the face; the edge of the form shadow is soft yet firm.
3. Sharp Edges: Sharp edges can be found at the edge of the cast shadow or where there is extreme contrast, such as dark hair against the forehead in light.
4. Lost Edges: Lost edges occur where the separation between two objects is so close in value that you cannot see where one ends and the other begins, such as the shadow side of dark hair against a dark background.
Ultimately edges and value are relative, and the variations in light and shadow are infinite within nature, so it's best to always carefully observe what is in front of you.
When doing these portraits I had to keep in mind the way shadows were cast on the faces. Hard or sharp edges on a face make it looks older but softening the edges to firm makes even an older person look more youthful. I find when doing portraits, you get paid better by being flattering and bringing back youth.