Setting up a CCTV camera system is not something to be taken lightly. It is a significant expenditure and should be thought through before a single pound is spent. The most important part of any CCTV system is the camera as it provides the eyes of the operation, so to speak. The key to buying the right CCTV camera is not simply in going out and buying the biggest or most expensive model on the market.
The key is to start by identifying the needs a camera has to meet. Once those needs are known, it becomes easier to find the right camera, as opposed to spending a large amount of time trying to select a camera without really knowing how or why it will be used. Knowing what matters to a given purchaser not only speeds the decision process, but also helps to ensure they make the right CCTV camera purchase decision. Therefore, the key is knowledge, knowing what to look for in order to meet the user’s needs.
How a CCTV Camera Works
Most CCTV, or closed-circuit TV cameras used in home security work, are solid-state electronic devices that are connected to a central recorder rather than broadcasted over the air. It is, therefore, a closed circuit, broadcasting to a specific location, rather than to anyone in range. The camera itself is usually made up of the following main components: lens, sensor, and digital signal processor, or DSP. In simplest terms, the lens focuses the light that is to be imaged onto the sensor, which then passes it to the DSP which converts it into a TV signal. This signal is then transmitted to a central location either by wire or wirelessly for storage and viewing.
Factors to Consider When Purchasing a CCTV Camera
There are a number of important factors to consider when purchasing a new CCTV camera, most of which map to one or more of the basic hardware components, so understanding the components and how they affect the CCTV camera’s performance is an important part of knowing what to look for.
Choosing the Right Lens
The lens is what gathers the light for the sensor. Everything the viewer sees, or that gets recorded on the DVR comes through the lens. It determines the distance at which a car’s number plate can be read, and a face can be recognised because the lens controls focus. In many cases, a better lens is more helpful than a higher output resolution, as the output is always limited by the input, and the lens determines the input.
Buyers should also look for a zoom lens. Some CCTV cameras come with digital zoom, where others have optical zoom, handled by the lens. Whenever possible, buyers should opt for optical over digital zoom. The problem with digital zoom is that it provides no more information than was in the original image. Optical zoom can actually add new information as it changes which light reaches the sensor.
Choosing the Right Sensor
Not all digital sensors are created equal. There are two main things to look for when studying the sensor specifications of a given CCTV camera: the first is the sensor type, the second is the sensor size. Most CCTV sensors are either CMOS or CCD. CMOS is less expensive and uses less power than CCD, but it is less sensitive and does not produce as clear an image, which can be particularly problematic when using the camera for identification purposes. One result of this is that CMOS-based sensors require more signal processing to produce a clear image.
The other important factor is the sensor size. The larger the sensor, the more light it can process, and the higher quality image it can produce. Most CCTV camera sensors come in one of two sizes: 1/4 inch, which measures 3.2 mm by 2.4 mm, and 1/3 inch, which measures 4.8 mm by 3.6 mm; giving it over twice the surface area of the smaller sensor. A larger sensor not only gathers more light, but in doing so gives the DSP more data to work with, which is especially helpful with the less capable processors used in budget cameras.
Choosing the Right Output Resolution
One very common specification for CCTV cameras is the number of horizontal lines of TV resolution it can output, or its TVL. This can range anywhere up to 700TVL, with many cameras coming in between 380TVL and 540TVL. Some experts recommend 420TVL as a minimum, but this is not always the case. While a high resolution is nice to have, the output depends on the input, so if the lens and sensor cannot match the output resolution, which is determined by the DSP, then the extra resolution is wasted. What matters most is having enough resolution to clearly display any image the camera can produce. Anything beyond that is unnecessary.
CCTV Camera Types
Not all CCTV cameras are the same size and shape. Different uses require different capabilities, and so there are different kinds of cameras to meet those needs. The following table shows the three basic types of cameras and some of their common uses.
CCTV Camera Type
|Bullet Camera||These small cylindrical CCTV cameras are often used in environments where discretion is important, but there is no need to permanently install the camera in a protective dome. They work well in shops and service areas when there is a need to monitor the staff|
|Dome Camera||A CCTV dome camera is an excellent choice for surveillance as it not only protects the camera from casual vandalism, but also provides a degree of security as it is often impossible to tell where the camera is pointed|
|IR Day/Night Camera||While obvious in appearance, these cameras have the advantage of providing 24-hour outdoor coverage regardless of lighting conditions. They provide a colour image in the daytime, shifting to black and white for infrared viewing at night|
Which camera a given buyer wants to use depends on their goals and needs. Understanding those needs make choosing the right CCTV camera that much easier.
Choosing the Right CCTV Camera
When choosing the right camera for a given purchaser’s needs, there are several things the buyer should look for. The first is a lens that gives the user a clear image of the area covered by the camera from its mounting point. If the area under surveillance is not in focus, then there is no real point to monitoring it. The next feature is the sensor, whenever possible buyers should go for the 1/3 inch CCD sensor as this provides the most information for the DSP to process. The final feature of the camera itself is the output resolution. While many companies may put this feature first, its usefulness is limited by the components in front of it.
Once the hardware capabilities have been determined, the next step is to decide which type of camera best fits the user’s needs. Those covering large outdoor areas, such as homeowners wanting to cover their property, may want to consider a day/night camera. Bullet cameras work well for monitoring staff, while ceiling-mounted dome cameras are good for covering the entire premises of a shop or business.
There are a number of things to look for when buying CCTV cameras. Some are technical factors which apply to every situation regardless of the intended use: every camera can benefit from a better lens and high quality sensor. Other factors are more dependent on the intended use of the CCTV camera, as some types are more useful in some situations than others. A day/night camera is great for keeping an eye on visitors coming up the drive, but it may not be the best choice for monitoring staff or business premises.
Many businesses may be better served with either dome cameras covering the entire floor or small bullet cameras to monitor the staff. Regardless of the buyer’s needs, it pays to look for quality. Therefore, understand how CCTV cameras work and the importance of optical zoom as opposed to digital zoom makes it easier to recognise said quality. The most successful purchases are informed purchases, and knowing what to look for makes buying a CCTV camera much easier.