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60 en | FlexiDome2X
AR18-08-B010 | v1.0 | 2009.03 Installation Manual Bosch Security Systems
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.