Power window

Grading tools call them windows, masks or qualifiers depending on the software. Draw an oval over a face, feather the edge, and any adjustment applies inside it alone, so you can brighten the presenter without lifting the whole room with them. Attach the shape to the tracker and it follows the subject through the shot. The commonest use is a soft vignette pulling half a stop off the corners. Two signs of a heavy hand: a visibly lighter oval around somebody's head, and a shape that drifts off the face when they move.