In order to understand the range of cameras available to the general market, and useful for ordinary consumer applications, this article is divided into three sections: camera types, lenses, and technology types.
For readers who are new to the topic of CCTV, mention should be made of the term. The term is an acronym for “closed-circuit television.” Other terms are used interchangeably that mean virtually the same thing: “security camera,” “surveillance camera,” “spy camera,” and “video camera.” There are some nuances in the meanings, perhaps, but they are very minor. There is no intention in this article to differentiate between them.
Types are basically a reference to the camera body style. There are three basic types for ordinary use: box cameras, dome cameras, and bullet cameras. There is an additional type called a “board camera,” getting its name from the fact that it attaches directly to a circuit board, without a body. They are used in applications such as ATM machines and not for everyday consumer applications; therefore, the discussion will be limited to the three main camera body types listed above.
The camera body of a box camera, as the name suggests, is in the shape of a box. The camera and lenses are normally bought separately. As they do in a still camera, the lenses are attached to the body and are easily changed if the application requires it.
Box cameras are known for giving high quality images, and with some of the higher specifications, the box cameras are often preferred in low light conditions.
The camera body and lenses for box cameras are more vulnerable to weather conditions and vandalism when mounted unprotected. The body of the box camera is not designed to withstand the elements, making it necessary to enclose the camera in weatherproof and vandal resistant housings.
Housings are designed to protect the camera, and the housing itself has some available features that make them a desirable choice. Some housings come with a heater/blower function that protects the camera from freezing temperatures and ice. The housings come with ratings from NEMA, the National Electronics Manufacturers Association, to give consumers guidance on selecting the best housing for the application.
Box cameras are versatile because of the ease with which the lenses are interchangeable, and the choices that can be made with housings. With the additional advantage of having some of the best specifications in the market, box cameras are still preferred by many users of security cameras.
The dome camera is the one commonly seen in public buildings. They are easily spotted because of their dome shape, often with a blue or gray tinted cover. They can be mounted on walls as well as ceilings, and with the proper housing and mounts, they can be mounted as a pendant or on poles.
Unlike the box camera type, dome cameras come in one piece. The lens is internal to the camera body. Though several choices of lenses are available, normally a dome camera’s lens is not changed once it is purchased and mounted. When buying a dome camera, it is important to know the range of distance that the camera will be watching, the lighting conditions, and any other dynamics that exist in the application. Changing lenses on a dome camera is impractical.
In the lens discussion below, there will be more said about the types of lenses. For the current discussion, however, let it be known that the lenses, though internal to the dome camera, should be adjusted and tested while installing. Removing the cover is required, and it is accomplished easily. Changing the lens is difficult and impractical, not the adjustment of the lens.
Another common body type for cameras is the bullet camera. These are cameras that come with the lens already installed, as in dome cameras, and they are already shrouded with an external housing.
Bullet cameras are most often seen in outdoor applications such as building perimeters, light poles, public gathering areas, concourses, and many other areas that are susceptible to weather and vandalism.
Lens choices for bullet cameras are generally the same as with box and dome cameras, and they are most always accompanied with infrared LEDs to give a reddish light in total darkness so the camera can see in the dark.
Quick Word About Infrared (IR) Options vs. Day/Night (DN) Cameras
Infrared LEDs are common, either in cameras or external housings, in most camera types. Buyers should be aware, however, that in many cases, in low light conditions, a day/night camera is preferable to an IR (infrared) camera. The day/night cameras on the market, especially in box cameras, often capture better images than infrared in low light conditions.
Why is this? Infrared LEDs are triggered by darkness. The lens in IR cameras is usually not capable of seeing in low light conditions. If the ambient light is bright enough, as it often is, even though the buyer thinks it is a dark condition, the IR LEDs may not be triggered, or may be ineffective. In total darkness, however, when there is no ambient light, such as moonlight or street lamps, infrared cameras are the best choice. Again, knowing the conditions is vital to making the right choice.
There are many specifications for lenses that may make one a better choice than others, but generally speaking, there are just a few basic lenses that need to be discussed here.
A fixed lens has only one focal length, which means that the lens is fixed on one space, with no capacity for adjusting the focus. If the optimal distance for a certain lens is to focus on ten feet away from the camera, it will see the ten feet distance very well. However, the further away from the ten feet distance the view gets, whether it is seven or thirteen, nearer or closer, the lens loses its focus.
A varifocal lens is one that can be adjusted within a certain range. It has a variable focal length. Do not be confused with the zoom function, which is discussed next, because it does not change on the fly. It simply means that the lens can be adjusted at the time of installation within a range of settings to accommodate variable distances.
The advantage of the varifocal lens is that a person can choose cameras that are uniform in appearance and function while still having the flexibility to focus each one for its own particular application. Having the focal length adjustment available keeps the buyer from having to replace a camera if the distances are different from what they had planned. There is so little cost difference between the two types of lenses, it is impractical not to use varifocal camera lenses.
Some lenses come with a zoom function that is controllable from a keyboard by an operator. It allows the operator to zoom in, or to bring an image closer, for a better look. The zoom function for camera lenses operates within the limitations of its designs. If it is a 10x optical zoom, for instance, it means the lens can be zoomed in at ten times the magnification of its basic position. If the focal length is 5mm, the zoom feature on a 10x zoom lens could zoom in to a 50mm range, giving a narrower field, but presenting a larger image for inspection.
PTZ cameras are the thoroughbred of the industry. Combining the zoom function with the ability to pan (side-to-side movement), and tilt (up and down movement), the PTZ offers maximum versatility in application.
Normally, the PTZ cameras are housed in domes, though they are typically larger than standard dome cameras.
A PTZ camera comes with a higher price, but it comes with a much higher better versatility. A PTZ camera is an excellent tool for watching large areas, such as parking lots, stadiums, junctions of major concourses within a building.
A PTZ controller is operated from a keyboard or joystick, and through the system software, an operator can switch among PTZs to control one, and then another, camera very quickly.
Another feature worth mentioning here is the auto-tracking function of some PTZ cameras. This is a setting that allows the user to set the PTZ function on automatic so that if a movement takes place within the camera’s view, the camera will track the movement, zoom in, and watch the movement until it is complete. It is a little more complicated than this, however, because a second movement, such as a car traveling in an opposite direction from another, may cause the auto-tracking feature to change over and watch the wrong car. Again, buyers should be cautious in selecting the additional functions. In most cases, there are downsides to making the wrong selection.
There are two basic types of technology that are used in the processing, or encoding, of images: analog, and IP (Internet protocol).
Analog is the tried and true technology that has been around since video cameras have existed. In the CCTV world, analog technology is used to transmit captured video footage to a digital video recorder (DVR) that encodes the captured images into digital format for viewing.
Analog cameras do not themselves encode, or digitize, the images. This work is done by the DVR, or a computer based DVR capture card.
The IP camera is a newer generation of security cameras. Offering higher resolutions of 1, 3, or 5 megapixels, or even higher, many companies promote IP cameras as if analog technology will eventually go away. As a side note, high-definition (HD) technology in analog varieties is making analog very attractive still, primarily because of legacy issues and costs.
In the IP camera, the encoding is done at the camera. In other words, the image is digitized as it appears in the lens, before it is passed along to the network video recorder (NVR) where it is decoded for viewing.
One of the biggest advantages of IP cameras is that they can be implemented wherever a network already exists. There are downsides, however. Unless the bandwidth is large enough to handle the constant feeding of several IP cameras, a network can be slowed down considerably, causing a larger investment in infrastructure to be necessary. Bandwidth can be managed, however, by setting cameras only to show footage when certain triggering events take place.
One common misconception about choosing between IP and analog cameras is the notion that remote access, or viewing, is only possible by using IP cameras. This is simply not true.
Confusion exists on the issue because of the term “IP” and its common use in network jargon. Both IP and analog are capable technologies for offering remote viewing. The IP address of a DVR (analog) allows remote access so that cameras can be viewed over the DVR. IP cameras can be viewed remotely by going directly to an assigned IP address for the camera; however, in many cases, even in IP technology, it is more advantageous to go through the video management software at the NVR so more control can be gained.
Wireless cameras are available for special needs. There are still infrastructure costs for transmitters and receivers, even though wiring is eliminated to the camera. Practicality is still a concern, and the application will dictate whether wireless is the answer.
Explosion-proof cameras are often brought into the CCTV discussion as well. One misconception about these cameras is that they will not explode if something like a plant explosion occurs. This is a misunderstanding. The meaning of “explosion-proof” is that the camera will not explode in special environments where gases might penetrate other types of housing and set off an explosion within the electronics of the camera. It does not mean the camera will survive a bomb. Explosion-proof cameras are, in essence, a tag placed on the types of housings, rather than the camera inside them.