1. A camera, comprising: an infrared (“IR”) imaging subsystem configured to obtain IR images, the IR imaging subsystem having an IR detector; a first visual imaging subsystem configured to obtain a first visual image of an object in a scene, the first visual imaging subsystem having a first visual light detector; a second visual imaging subsystem configured to obtain a second visual image of an object in a scene, the second visual imaging subsystem having a second visual light detector, wherein the first and second visual images have a parallax, or displacement, dependent on the distance to the object and based on a known parallax function; and a processor configured to determine the parallax, or displacement, 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, based on at least part of the first and second visual images.