This paper is concerned with how perceptions of objects and surroundings are affected by the directional nature of lighting. The changing appearances of isolated objects are examined, and also how these relate to more general perceptions within a room. The concepts of the Sharpness and the Flow of Light are proposed to describe the principal aspects of these effects, and the physical parameters to which they may be related are identified. Means of prediction and measurement are described briefly, and sources of recommendations expressed in these terms for the guidance of lighting designers are referred to.