A light-tight box that receives light from an object or scene and focuses it to form an image on a light-sensitive material or a detector. The camera generally contains a lens of variable aperture and a shutter of variable speed to precisely control the exposure. In an electronic imaging system, the camera does not use chemical means to store the image, but takes advantage of the sensitivity of various detectors to different bands of the electromagnetic spectrum. These sensors are transducers that convert energy received in to an electronic or electrical effect (i.e., change of resistance, current, electromotive force, the emission of electrons); the signals are stored (now most significantly in digital form), and eventually displayed, most frequently on a cathode-ray tube. See also cathode-ray tube; orthicon; vidicon.