"Light Scallops
Light scallops can be an intentional or unintentional effect of a down-lighting plan. The last row of down-lights closest to the wall will cause light scallops, which if planned for can add visual interest to a space. The more diffuse the light source and trim are, the softer the scallop will be. For example a R/BR-lamp mounted in a flush-to-ceiling open trim, will barely create any scallop, while a R-lamp in a shallow white baffle will create a soft scallop, and a PAR lamp in a deep-black baffle trim will create a crisp scallop. You should be mindful of the horizontal location of the center of the scallops relative to architectural features such as cabinet frames, doorways, windows, etc."
http://www.grandlight.com/design.htm