"John Smith's Leading Light evolves a sense of screen depth and surface through the simple agency of light. The film is shot in a room over a period of a day and records the changes in light through the single window. The image is controlled through the manipulation of aperture, of shutter release, of lens, but the effect is more casual than determined and the spectator is aware primarily of the determining nature of following sunlight." -- Deke Dusinberre, Perspectives on British Avant-Garde Film catalogue.

"Leading Light uses the camera-eye to reveal the irregular beauty of a familiar space. When we inhabit a room we are only unevenly aware of the space held in it and the possible forms of vision which reside there. The camera-eye documents and returns our apprehension. Vertov imagined a 'single room' made up of a montage of many different rooms. Smith reverses this aspect of 'creative geography' by showing how many rooms the camera can create from just one." -- A.L. Rees "Unpacking 7 Films" programme notes.