Penumbra

n. partly lighted area around any shadow

For other uses of the word "umbra", see Umbra (disambiguation). For other uses of the word "penumbra", see Penumbra (disambiguation). The umbra (Latin: "shadow") is the darkest part of a shadow. From within the umbra, the source of light is completely blocked by the object causing the shadow. This contrasts with the penumbra, where the light source is only partially blocked and there is only a partial shadow.
See more at Wikipedia.org...

Penumbra a blurred edge to an image, a halo effect, in an x-ray film caused usually by an overlarge focal spot exacerbated by a long object-to-film [more]Penumbra - Community and Resources

Noun
1. a fringe region of partial shadow around an umbra
(hypernym) shadow

n. penumbra, partly lighted area around any shadow