1. A camera comprising: an infrared (“IR”) imaging subsystem for obtaining IR images, the IR imaging subsystem having an IR detector; a first visual imaging subsystem for obtaining a first visual image of an object in a scene; a second visual imaging subsystem for obtaining a second visual image of an object in a scene, wherein the first and second visual images have a parallax dependent on the distance to the object and based on a known parallax function; and a processor for determining the parallax between the first visual image of the object taken by the first visual imaging subsystem and the second visual image of the object taken by the second visual imaging subsystem.