Video Surveillance Glossary of Terms [F]

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• » Fast lens [top]
  Having a larger iris (and smaller F-stop), a fast lens gathers and transmits increased light to a surveillance camera.
  
• » FCC (Federal Communications Commission) [top]
  This United States commission regulates communications by setting rates, controlling broadcast licensing, and testing electronic equipment to RF (radio frequency) transmission and related standards. 
  
• » Fence disturbance sensor [top]
  The perimeter fence around a site may have one of these installed around it for intrusion detection.  These sensors can be interfaced with a CCTV switcher so that specific cameras are activated in an area where the disturbance is detected.
  
• » FI (Fixed Iris) [top]
  These widely used fixed focal length iris lenses are inexpensive and are found in smaller types of fixed CCTV security cameras, usually small case or dome cameras. 
  
• » Fiber Optics [top]
  These high-speed computer-networking cables transmit data using light instead of copper.
  
• » Field [top]
  A field is one half of a frame, with 262.5 lines in the NTSC standard.  Interlaced television monitors display their images in two steps.  The first step paints every other line, while the second paints the remaining ones.  Progressive monitors present a complete field with each frame.  Sixty fields are transmitted each second. 
  
• » Field of view [top]
  This is the total height and width of the view seen through the lens.
  
• » Firewall [top]
  A firewall is a software or hardware application installed on a home or office computer that is intended to prevent unauthorized users from accessing that computer.  With hacking and network intrusions on the rise, they are becoming essential in protecting private information.  Four popular types of firewall are packet filtering, application gateways, circuit-level gateways, and proxy servers.  Although they can be difficult to configure correctly, they are a critical component to protect unauthorized access and hacking of IP based surveillance systems that are LAN based.
  
• » Flange back [top]
  This refers to the distance from lens flange (the beginning of the lens mount) to the focal plane.  The flange back measurement for C-mount lenses is 17.52mm, while CS-mount is 12.5mm.
  
• » f-number [top]
  This is used to indicate image brightness as formed by the lens and controlled by the iris.  The smaller the f-number, the brighter the image is.
  
• » Focal Length [top]
  Focal length is measured in mm or inches, and is the distance between the optical center of the lens and the point on which it focuses.  A lower focal length results in less magnification with a greater field of view, and vice versa for longer focal lengths.  Security cameras usually have a focal length of ¼”, 1/3”, or ½”.
  
• » fps (Frames Per Second) [top]
  In the field of video surveillance, fps means the number of frames a DVR is able to capture per second.  Three steps are required: video capture, compression, and storage.  Each step affects a DVR’s true fps number.  The use of DSP chips in both IP cameras and DVRs can assist in the optimization of fps.
  
• » Frame [top]
  One complete picture is called a frame, and it contains 525 lines (NTSC) or 625 lines (PAL). 
  
• » f-stop [top]
  The light gathering ability of a lens (known as a camera lens aperture setting) is indicated by an f-stop.  Using a smaller f-stop number results in a greater amount of light passing through the lens, as well as a shallower depth of field.
  
• » FTP (File Transfer Protocol) [top]
  FTP is a client/server protocol used for the exchange of data between computers.  Network cameras with an embedded operating system use FTP to send camera images to an authorized user’s computer or web site.

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