Types of network cameras

Network cameras can be classified in terms of whether they are designed for indoor use only or for indoor and outdoor use. Outdoor network cameras often have an auto iris lens to regulate the amount of light the image sensor is exposed to. An outdoor camera will also require an external, protective housing unless the camera design already incorporates a protective enclosure. Housings are also available for indoor cameras that require protection from harsh environments such as dust and humidity, and from vandalism or tampering. In some camera designs, vandal and tamper-proof features are already built-in and no external housing is required.

Network cameras, whether for indoor or outdoor use, can be further categorized intofixed, fixed dome, PTZ, and PTZ dome network cameras.

 

 

Fixed network cameras

A fixed network camera, which may come with a fixed or varifocal lens, is a camera that has a fixed field of view (normal/telephoto/wide-angle) once it is mounted. A fixed camera is the traditional camera type where the camera and the direction in which it is pointing are clearly visible. This type of camera represents the best choice in applications where it is advantageous to make the camera very visible. A fixed camera usually enables its lens to be changed. Fixed cameras can be installed in housings designed for indoor or outdoor installation. 

Fixed dome network cameras

A fixed dome network camera, also called a mini dome, essentially involves a fixed camera that is pre-installed in a small dome housing. The camera can be directed to point in any direction. Its main benefit lies in its discreet, non-obtrusive design, as well as in the fact that it is hard to see in which direction the camera is pointing. The camera is also tamper resistant.

 

 

One of the limitations of a fixed dome camera is that it rarely comes with an exchangeable lens, and even if it is exchangeable, the choice of lenses is limited by the space inside the dome housing. To compensate for this, a varifocal lens is often provided to enable the camera’s field of view to be adjusted.

 

 

Fixed dome cameras are designed with different types of enclosures such as vandal-resistant and/or IP66-rated for outdoor installations. No external housing is required. The mounting of such a camera is usually on a wall or ceiling.

PTZ cameras and PTZ dome cameras

A PTZ camera or a PTZ dome camera can manually or automatically pan, tilt and zoom in and out of an area or object. All PTZ commands are sent over the same network cable as for video transmission; no RS-485 wires need to be installed as is the case with an analog PTZ camera.

Some of the features that can be incorporated in a PTZ camera or a PTZ dome camera include:

• Electronic image stabilization (EIS). In outdoor installations, PTZ dome cameras with zoom factors above 20x are sensitive to vibrations and motion caused by traffic or wind. EIS helps reduce the affects of vibration in a video. In addition to getting more useful video, EIS will reduce the file size of the compressed image, thereby saving valuable storage space.
• 3D privacy masking. 3D privacy masking is supported in most  PTZ dome cameras and enables selected areas of a scene to be blocked or masked from viewing and recording. It allows masking to be maintained even as the camera’s field of view changes through panning, tilting and zooming as the masking moves with the camera’s coordinate system.

With built-in privacy masking (gray rectangle in image), the camera can guarantee privacy for areas that should not be covered by a surveillance application.

• Preset positions. Many PTZ cameras and PTZ dome cameras enable a number of preset positions, normally between 20 and 100, to be programmed. Once the preset positions have been set in the camera, it is very quick for the operator to go from one position to the next.
• E-flip. When a PTZ dome camera is mounted on a ceiling and is used to follow a person in, for example, a retail store, there will be situations when a person will pass just under the camera. When following through on the person, images would be seen upside down without the E-flip functionality. E-flip electronically rotates images 180 degrees in such cases. It is performed automatically and will not be noticed by an operator.
• Auto-flip. PTZ cameras, unlike PTZ dome cameras, do not normally have a full 360-degree continuous pan due to a mechanical stop that prevents the cameras from making a continuous circular movement. However, with the Auto-flip functionality, a PTZ network camera can instantly flip the camera head 180 degrees and continue to pan beyond its zero point. The camera can then continue to follow a passing person or object in any direction.
• autotracking. autotracking is an intelligent video functionality that will automatically detect a moving person or vehicle and follow it within the camera’s area of coverage. Autotracking is particularly beneficial in unmanned video surveillance situations where the occasional presence of people or vehicles requires special attention. The functionality cuts down substantially the cost of a surveillance system since fewer cameras are needed to cover a scene. It also increases the effectiveness of the solution since it allows a PTZ camera or PTZ dome camera to record areas of a scene with activity.

Although PTZ cameras and PTZ dome cameras may share similar functionalities, there are differences between them:

• PTZ network cameras do not have a full 360-degree continuous pan due to a mechanical stop. It means that the camera cannot follow a person walking continuously in a full circle around the camera. Exceptions are PTZ cameras that have the Auto-flip functionality; for example, AXIS 215 PTZ Network Camera.
• PTZ network cameras are not made for continuous automatic operation or so-called guard tours where the camera automatically moves from one preset position to the next.

Mechanical PTZ network cameras

Mechanical PTZ cameras are mainly used indoors and in applications where an operator is employed. The optical zoom on PTZ cameras typically ranges from 10x to 26x. A PTZ camera can be mounted on a ceiling or wall.

Non-mechanical PTZ network cameras

A non-mechanical PTZ network camera,  offers instant pan, tilt, zoom capabilities with no moving parts, so there is no wear and tear. Using a wide-angle lens, it offers a wider field of view than a mechanical PTZ network camera.

Images from a non-mechanical PTZ network camera. At left, a 140-degree overview image in VGA resolution; at right, image when making a 3x zoom.

A non-mechanical PTZ camera uses a megapixel image sensor and allows an operator to instantly zoom in on any part of a scene without any loss in image resolution. This is achieved by presenting an overview image in VGA resolution (640x480 pixels) even though the camera captures a much higher resolution image. When the camera is instructed to zoom in on any part of the overview image, the camera uses the original megapixel resolution to provide a full 1:1 ratio in VGA resolution. The resulting close-up image offers good details with maintained sharpness. With a normaldigital zoom, the zoomed-in image often loses detail and sharpness. A non-mechanical PTZ camera is ideal for discreet, wall-mounted installations.

PTZ dome network cameras

 

PTZ dome network cameras can cover a wide area by enabling greater flexibility in pan, tilt and zoom functions. They enable a 360-degree, continuous pan, and a tilt of usually 180 degrees. PTZ dome cameras are ideal for use in discreet installations due to their design, mounting (particularly in drop-ceiling mounts), and difficulty in seeing the camera’s viewing angle (dome coverings can be clear or smoked).

 

A PTZ dome network camera also provides mechanical robustness for continuous operation in guard tour mode, whereby the camera automatically moves from one preset position to the next in a pre-determined order or at random. Normally up to 20 guard tours can be set up and activated during different times of the day. In guard tour mode, one PTZ dome network camera can cover an area where 10 fixed network cameras would be needed. The main drawback is that only one location can be monitored at any given time, leaving the other nine positions unmonitored.

 

The optical zoom of a PTZ dome typically ranges between 10x and 35x. A PTZ dome is often used in situations where an operator is employed. This type of camera is usually mounted on a ceiling if used indoors, or on a pole or wall of a building in outdoor installations.