An apparatus (30) and associated method determine a vehicle occupant characteristic. An imager (32) collects a first image of an occupant location while the occupant location is subject to a first lighting condition. A light source (38) provides light onto the occupant location. The imager (32) collects a second image of the occupant location while the occupant location is subject to the first lighting condition and the provided light. A subtractor device (50) generates a third image of the occupant location indicative of the difference between the first and second images. An image processing device (52) processes the third image to determine the vehicle occupant characteristic.