Light Graffiti, London, United Kingdom

Light painting can be done interactively using a webcam. The painted image can already be seen while drawing, e.g. using the monitor or a video projector. Additional digital processing can be applied directly in the computer. This can be used e.g. to enable light painting during the day. A free software for that is myLightPainting.
Using projections
A technique known from light art is to project images on to irregular surfaces (faces, bodies, buildings etc.), in effect "painting" them with light. The first time The London Trophy for artistic photography was awarded for a colour photograph was in 1967 for a photograph by John N. Cohen that consisted of a colour portrait blended with a negative of a tulip, created by photographing these projected images.