CAMERA GUIDE CAMERAS Having planned where you are going to put cameras you need to decide which cameras you are going to require to cover your areas and give the necessary view. Cameras, together with appropriate lenses, will be able to view any area that is required, so the main choices to make is what type of camera you require, the quality of the pictures and the field of view. Most cameras are powered by a 12 volt power source, with PTZ Cameras requiring 24 volts. All modern cameras are digital. Cameras come in many variations, some very basic descriptions to assist you:
· · · · · · · ·	Internal Cameras - made to be used indoors only, it may seem obvious but there is a premium for external cameras (see below) and often internal cameras are used outside in an effort to save money...they don't last long outside. Many of the internal cameras are described as "Dome" cameras which should not be confused with "PTZ Dome Cameras" (see below). External Cameras - made to be used outdoors, weatherproof with sealed cables and tough bodies. IR (Infra-red) - cameras that have the addition of LED's around the lens area which aid viewing in the dark. Box cameras - the classic shaped cameras that are made for internal use only but can also be used inside an "External Housing" to make them weather proof so they can be used externally. Day/Night Cameras - During the day they display in colour and at night they automatically switch to monochrome (black & white). Monochrome gives much better definition in the dark and particularly in infra-red light as colours are very difficult to distinguish in the dark. Vandal or Attack Resistant Cameras - used internally or externally where they are likely to come under attack. Covert Cameras - These are cameras that are hidden inside everyday objects such as alarm PIR's,clocks,smoke detectors etc. they can be used in areas that need to be monitored discretely without obvious knowledge such as stockrooms. PTZ Dome Cameras - Pan, Tilt & Zoom (PTZ) cameras allow for movement of the actual camera, these are used mostly externally in open areas. They are used internally where there is a large space to monitor like a Shopping Centre or large Supermarket. PTZ Domes are expensive to install as they require controlling equipment at the display end.
Resolution of CCTV cameras is measured in TV Lines (TVL) the standard entry level camera will have a resolution of around 330 TVL with High Resolution cameras having 400 TVL or over, but, the higher resolution cameras have a premium. Light (The Friend & Enemy of Cameras) Most CCTV cameras manage the normal environmental ambient light conditions for which they are designed very well, they can adjust to rapid changes in the intensity of the light conditions automatically but they struggle with the very bright (direct) light and the very dark. A camera faced with more brightness than it can handle will shutdown to protect itself and most Day/Night specified cameras will switch to black & white at 0.5 lux. The minimum illumination level of camreas is shown in lux. Light levels are measured in lux. In order to give some understanding to lux. levels please see below: Sunny Day 50,000 - 55,000 lux Cloudy Day 5,000 - 10,000 lux Commercial Internal Lighting 500 lux Stadium or Street Lighting 30 - 50 lux Full Moonlight 0.5 - 0.75 Where the ambient light is insufficient to allow a camera to work normal lighting can be used to supplement the background lighting, remember that "light pollution" can cause problems and in these cases Infra-Red (IR) lighting may be preferable. Day/Night cameras come with integral IR lights. LENSES Most dome & IR cameras come with a lens fitted but this may not give the required view, most lenses can be changed to allow a flexible solution to your needs. Lenses come in two main types "fixed" which means it has a fixed focal length and "vari-focal" which means it has a variable focal length, all lenses can be focused to some degree. Most box cameras do not come with a lens fitted and so a lens must always be added unless it states that a lens is included. Deciding which lens you require can seem complicated, a general rule of thump is that a wide angle lens of 2.8mm will give a wide field of view but not much depth of field a narrow angle lens of 12mm will give a narrow field of view but a deep field of view, so the lower the number the wider the field of view. Beware that very wide lenses (under 2.5mm), sometimes called "fisheye lens" will give distortion around the edges. The most common focal length for lens is 3.6mm.