Industry Terms
ANGLE OF VIEW - May be expressed in Diagonal, Horizontal, or Vertical. Smaller focal lengths give a wider angle of view.APERTURE The opening of the lens that controls the amount of light reaching the surface of the pickup device. The size of the aperture is controlled by the iris adjustment.
AUTO-IRIS LENS A lens with an electronically controlled iris. This allows the lens to maintain one light level throughout varying light conditions.
CAMERA FORMAT The approximate size of a camera image pickup device. This measurement is derived from the diagonal line of a chip or the diameter of the tube.
COVERT CAMERAS Cameras used for viewing areas of suspicious activity. These small cameras are commonly used in objects such as: smoke detectors, motion detectors, sprinkler heads, clocks, exit signs or change machines.
DEPTH OF FIELD The regions in front of and behind the focused distance where the image remains in focus. Lens aperture and scene lighting will greatly influence the depth of field.
FIELD OF VIEW The horizontal or vertical scene size at a given length from the camera to the subject.
FOCAL LENGTH The distance from the center of the lens to a plane at which point a sharp image of an object viewed at an infinite position. The focal length determines the size of the image and angle of field of view seen by the camera through the lens.
HUNTING An industry term used to describe an auto-iris lens inability to stabilize under certain light conditions.
IRIS A mechanical diaphragm which is controlled manually or automatically to adjust the lens aperture.
LENS FORMAT The approximate size of a lens projected image. In most cases the lens will project a image slightly greater than the designated image size to insure the pickup device is completely covered. It is recommended that camera and lenses are the same format size
LENS SPEED Refers to the lens aperture or its ability to transmit light. This is measured in F-stops.
MANUAL IRIS LENS A lens with a manual adjustment to set the iris opening (aperture) to a fixed position. This type of lens is generally used in fixed lighting conditions.
PINHOLE LENS Lenses used primarily in covert applications where the camera/lens must remain out of sight.
TELEPHOTO Telephoto is a term used to describe lenses that have a high focal number causing the reproduced image to appear larger than human eye reproduction.
TRACKING A zoom lens ability to remain in focus throughout the entire zoom range.
VARI-FOCAL A low cost version of a zoom lens designed to meet installers needs for versatility. This lens does not have the ability to track from wide to telephoto.
VIDEO TYPE LENS An auto-iris lens with internal circuitry for processing of the video signal which controls the iris movements.
ZOOM LENS A lens with the ability to change its focal length manually or through the use of a controller to cover a variety of needs.