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Guide to CCTV - Introduction There are a vast range of CCTV products and prices

Guide to CCTV - Introduction There are a vast range of CCTV products and prices to choose from in the marketplace but little information to help discriminate between them. Here are some examples. A camera described as good in low-level light will often not produce images at night unless there is additional lighting. There may be no explanation or qualification of the term low- level light. Wireless cameras can be fitted in minutes as there are no cables to run back to your TV or monitor. However, the cameras still require a power source and while battery power is convenient the consumption is great giving a working time of less than 24 hours (as low as 2 on some products tested). Wireless connectivity is nevertheless very useful for some applications as described later. There are plenty of professional CCTV installers who will give you a site survey and recommend appropriate products but, of course, you pay for this service. Modern technology has now made CCTV products much more affordable and they can be very easy to fit for the average DIY person. This guide will help you choose the correct products and show some simple methods of fitting complete systems to domestic and commercial properties. DIY CCTV Systems can easily be fitted by people with moderate DIY skills. Cameras The traditional CCTV camera has a very industrial style and, therefore, many people would not find this suitable for fitting to their homes or shops. This traditional style is actually a housing that is designed to keep the camera dry and within the recommended operating temperature. Thermostatic heating elements within the casing also reduce condensation and misting. These types of top-end cameras are usually specified without a lens, this being chosen to give the required focal length and field of view. Motorised pan and zoom lenses allow an observer to follow or move in closer to the person or object in view. We can supply these types of cameras to those of you who do not find the price prohibitive. Please contact 2SEETV with your requirements. Fortunately, for those of us with more down-to-earth budgets modern technologies now allow the production of cameras with excellent performance. There are two common types of CCTV cameras, CMOS and CCD (see glossary of terms). CMOS based cameras are generally cheaper but do not produce as clear or sharp images as CCD cameras. There is little point installing a CCTV camera if it is incapable of allowing you to easily identify who or what is being captured and recorded. CCD cameras provide pin-point clarity and should be specified wherever possible. The KT&C, Everfocus and Concept camera range, in general use the Sony CCD chipset. Beware of competing products that do not state whose chipset is used. Integrated cameras and lenses often referred to as "bullet cameras" are sealed to prevent ingress of moisture. The sealing is so good that they can be permanently immersed to some considerable depth in water if required. Bullet cameras do not need a heater and their small size makes them highly suitable for fitting to domestic and commercial properties. It is not possible to make adjustment to these cameras because they are permanently sealed. Most of the bullet cameras in the 2seetv store are fitted with a 3.6mm lens which gives a 72 deg angle of view which is suitable for most domestic and small commercial properties. Please contact us if you require alternatives. Choosing a Camera Specification The main criteria of a camera's performance are its sensitivity and resolution. Secondary considerations are colour or monochrome and indoor or outdoor suitability. Sensitivity is the camera's ability to respond to light levels. Resolution defines the amount of picture detail in the image produced by the camera. Camera resolution This is expressed as the number of television lines that the camera is capable of producing. For example the KT&C monochrome bullet camera is classed as 420 lines or usually 420 TVL. The comparable colour model is 380 TVL These are typical figures for CCD cameras, CMOS cameras are usually lower. Higher resolution cameras of over 500 TVL are available for select applications. For example, trying to read the number plate of a fast moving car would need the best resolution affordable. You should be able to read a stationary number with a resolution of 380 TVL. Below 300TVL and using CMOS cameras even facial features will be difficult to distinguish. These are very broad guidelines and also depend on the light levels and shadow conditions. Indoor/Outdoor Cameras If a camera is to be sited outside and is not going to be mounted in an enclosure it must be classed as weather resistant. The cable entry points are sealed and most bullet cameras come with trailing leads that allows the connections to be made inside the building. Typically 18ins (45cm) should be sufficient. One bullet camera under review had only a few centimetres of cable. This means the connection would be exposed to the rigours of the weather. Needless to say this model did not meet the selection criteria of 2seetv. The strength and durability of the casing is difficult to quantify but we have rejected cameras with flimsy plastic enclosures, particularly wireless cameras where the antenna dish looks like it could be easily damaged. The range of KT&C bullet cameras have strong aluminium bodies and sealed cable entry points and were selected for these features. Light Levels Choosing the correct camera to operate in the ambient light conditions is possibly the most important although most tricky specification to understand. Light levels are usually measured in Lux. This is a measure of the light energy arriving on an area 1m2 of surface per second. Typical light levels are: Full Summer Sunlight: 50,000 Lux Dull Daylight: 10,000 Lux Shop/Office environment: 500 Lux Dawn/Dusk: 1 - 10 Lux Main Street Lighting: 30 Lux Side Street Lighting: 0.5 - 3 Lux The golden rule when deciding which camera to use for a given lighting condition is not to choose one that will only just give a picture. Try to give the camera approximately 10 times its quoted minimum scene illumination. Most cameras will be able to cope with excess light. The major problem is when they do not have enough light to produce a picture. The sensitivity of covert cameras with pin-hole lenses are often quoted as 0.1Lux @f1.4. This seems to indicate that the camera will work in ¼ moonlight. Actually the pin-hole lens will have an aperture ratio of something like f4 and so the camera will need approximately 1 Lux to produce a picture. Unless your house is directly under main-street lighting the light level is probably less than 1 Lux at the front and even lower at the back. Bright security flood lights in theory help but often produce dark shadows a short distance from the house. A monochrome camera rated at 0.05 Lux will produce reasonable results. Colour needs a little more. However, colour cameras achieve good night-time vision by switching to a monochrome mode. You will never get good night-time colour pictures without huge amounts of additional lighting. So think carefully about the added cost of colour over monochrome cameras. As most people are used to colour television it sets a standard so it is very common to still select a colour camera knowing it will switch to monochrome mode at night. Monochrome cameras respond well to additional IR (infra red) lighting. With this in mind true night-vision cameras include a ring of IR LEDs. Colour cameras also offer IR illumination but as stated previously will switch to monochrome at night even with the IR LEDs turned on. These are true night-vision cameras and are rate at 0 Lux. How to display the picture from more than one camera Most CCTV systems deploy several cameras so a method is required to view and record the images. Simple, says the professional, use a video switcher, a quad or a multiplexer. DVRs (digital video recorder) now have multiplexer built into them but it still useful to understand the basic principles. Here are the simple benefits of each system. Switcher A CCTV switcher is a unit that changes between camera pictures one at a time, the output being viewed on a monitor or passed to the recording device. As switchers can use any VCR to record in true real-time, the pictures which are captured can be of a very high quality. Many professionals under-rate switchers. The fact that they provide true real-time recording unlike a snapshot from a multiplexer means they provide a superior picture quality. This can sometimes outweigh the disadvantages that switchers can only record one picture at a time. When to use a switcher Use for low cost systems Advantages - Simple, low cost, good quality real-time pictures. Disadvantage - Can only record one camera at a time. Quadsplitters Quad units enable 4 camera pictures to be displayed on a screen simultaneously. When to use a quadsplitter They are useful uploads/Geographie/ guide-to-cctv.pdf