The photograph of the ball shows the quality of overcast light. The cast shadow has no definite edge. There’s no clear division between light and shadow unless the form turns on a hard edge.
Here’s an example of overcast light falling on the figure of David Balfour in the N. C. Wyeth illustration “On the Island of Earraid,” from Kidnapped. The planes of the figure’s skin and clothing get lighter where they face more toward the light sky. (The sharp tonal changes in the background are dramatic plane changes in the rock.)
Another example of overcast light is this portrait of a girl by William Bouguereau. The form doesn’t have a light side and a shadow side in the conventional sense. The vertical plane of the dress and the upper arm are both darker than the forearm and the leg of the dress, which catch more light because they face more upward.
The coolness of this light source is evident from the relatively warm shadow under the chair. Occlusion shadows require especially careful attention in diffuse light, often appearing as notably sharp accents in the work of Bouguereau and Rockwell.
Light and Form, Part 1
Light and Form, Part 2
Light and Form, Part 3
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More about all this in my book: Color and Light: A Guide for the Realist Painter