Bosch VDN-498V03-21 User Manual - Page 53

60 en | FlexiDome2X F F-Number The standard measure of the lens aperture, which is the iris diameter, divided by the focal length of the lens. The lower the maximum aperture (F-Number or F-Stop), the more light that passes through the lens. F-Stop See F-Number Field of View The measure of the visible area within the camera's field of view. The larger the focal length, the smaller the field of view. The smaller the focal length, the wider the field of view. Focal Length The distance from the optical center of the lens to the image of an object located at an infinite distance from the lens. Long focal lengths give a small field of view (e.g. telephoto effect), while short focal lengths give a wide angle view. I Infrared Illumination Electromagnetic radiation (light) with a longer wavelength than is visible to the human eye. IR illumination is prominent at dusk and dawn and in incandescent lamps. IR illuminators come in the form of lamps with the appropriate filters, LEDs, or lasers. CCD sensors are less sensitive to IR than visible light, but IR can significantly increase the total illumination level, leading to a much better image at low light levels. IRE (Institute of Radio Engineers) A measurement of video amplitude that divides the area from the bottom of sync to peak white level into 140 equal units 140 IRE equals 1V peak-to-peak. The range of active video is 100 IRE. AR18-08-B010 | v1.0 | 2009.03 Installation Manual Bosch Security Systems