A visual effect that occurs when the penumbras of two shadows overlap, creating a darker region that makes the shadows appear to bulge or blister toward one another. This happens because the overlapping areas of partial shadow block more of the extended light source than a single penumbra does. It is a critical consideration in multi-source lighting environments where overlapping shadows can create distracting visual artifacts on a backdrop.
Heard on the job
You need to adjust the key and fill angles to get rid of that shadow blister effect on the presenter's face.