1. A method of replacing an original background of a scene with a predetermined replacement background, said method comprising the steps of: making a first infrared (IR) image of the scene at a first time with first IR radiation having a first intensity illuminating said original background; measuring an intensity of IR radiation at each pixel of said first IR image; making a second IR image of the scene at a second time after deactivating said first IR radiation, by illuminating a foreground of the scene with a second IR radiation having a second intensity less than said first intensity; measuring an intensity of IR radiation at each pixel of said second IR image; generating a mask distinguishing said foreground from said original background by comparing the intensities of IR radiation at each corresponding pixel between said first and second IR images; making a digital visible light image of the scene at said second time by illuminating the scene with visible lighting; and replacing, in said digital visible light image, said original background with said predetermined replacement background to produce a modified version of the digital visible light image by applying said mask to the digital visible light image.