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5

Camera selection


For a successful installation, the selection of the correct camera is essential.

There are a lot of things to consider: coverage area and angle, operational requirements – detection/recognition/identification, environmental constraints, and more. If the camera will operate in specific, tough conditions, or be put in difficult areas when it comes to light, such as extremely dark environments or in environments with high contrast between light and dark areas, this also has to be taken into account.


Guideline for selecting a network camera:



1. Define the surveillance goal: overview or high detail


Overview images aim to view a scene in general or view the general movements of people. High detail images are important for identification of persons or objects (such as face or license plate recognition, point-of-sale monitoring). The surveillance goal will determine the field of view, the placement of the camera, and the type of camera/lens required.


2. Overt or covert surveillance


This will help in selecting cameras, housings, and mounts that offer a non-discreet or discreet installation.


3. Coverage area


For a given location, determine the number of interest areas, how much of these areas should be covered, and whether the areas are located relatively close to each other or spread far apart. The area will determine the type of camera and number of cameras required.

An area may be covered by several fixed cameras or a few PTZ cameras. Consider that a PTZ camera with high optical zoom capabilities can provide high detail images and survey a large area. However, a PTZ camera may provide a brief view of one part of its area of coverage at a time, while a fixed camera will be able to provide full coverage of its area all the time. To make full use of the capabilities of a PTZ camera, an operator is required or an automatic tour needs to be set up.

One of the unique benefits that network video brings to the video surveillance market is the ability to move beyond the traditional PAL/NTSC resolution and frame rate limitations, and experience high-resolution video with extreme image detail. HDTV, megapixel and standard resolution cameras have different application areas and benefits. For instance, if there are two, relatively small areas of interest that are close to each other, a megapixel or HDTV camera with a wide-angle lens can be used instead of two non-megapixel cameras.


4. Light sensitivity and lighting requirements


Cameras with auto-iris lenses, such as a DC-iris or P-iris, are required for outdoor environments. In addition, consider the use of day and night cameras, due to their light sensitivity or whether additional lighting or specialized light from sources such as IR lamps is needed. Keep in mind that because there is no industry standard for measuring light sensitivity, lux measurements on network cameras are not comparable among different network video product vendors.


5. Image quality


Image quality is one of the most important aspects of any camera, but it is difficult to quantify and measure it. The best way to determine image quality is to install various cameras and look at the resulting video images. If capturing moving objects is clearly a priority, it is important that the network camera uses progressive scan technology.


6. Resolution


For applications that require detailed images, megapixel or HDTV cameras may be the best option.


7. Compression


The three video compression standards offered in Axis network video products are H.264, MPEG-4 and Motion JPEG. H.264 is the latest standard and offers the greatest savings in bandwidth and storage.


8. Audio


If audio is required, consider whether one-way or two-way audio is needed. Axis network cameras with audio support come with a built-in microphone and/or an input for an external microphone and a speaker or a line out for external speakers.


9. Event management and intelligent video


Event management functionalities are often configured using a video management software program and are supported by input/output ports and intelligent video features in a network camera or video encoder. Making recordings based on event triggers from input ports and intelligent video features in a network video product provides savings in bandwidth and storage use, and allows operators to take care of more cameras since not all cameras require live monitoring unless an alarm/event takes place.


10. Networking functionalities


Considerations include PoE, HTTPS encryption for encrypting video streams before they are sent over the network, IP address filtering, which gives or denies access rights to defined IP addresses, IEEE802.1X to control access to a network, IPv6, and wireless functionality.


11. Open interface and application software


A network video product with an open interface enables better integration possibilities with other systems. It is also important that the product is supported by a good selection of application software, and management software that enable easy installation and upgrades of network video products. Axis products are supported by both in-house video management software and a wide variety of video management software solutions from more than 550 of its Application Development Partners.

Another important consideration, outside of the network camera itself, is the selection of the network video product vendor. Since needs grow and change, the vendor should be seen as a partner, and a long-term one at that. This means that it is important to select a vendor that offers a full product line of network video products and accessories that can meet the needs now and well into the future. The vendor should also provide innovation, support, upgrades and product path for the long term.

Once a decision has been made as to the required camera, it is a good idea to purchase one and test its quality before planning to order quantities of it.


Determining the coverage area


When selecting cameras, the field of view required should be defined. The field of view is determined by the focal length of the lens and the size of the image sensor; both are specified in a network camera’s datasheet.

A lens’ focal length is defined as the distance between the entrance lens (or a specific point in a complicated lens assembly) and the point where all the light rays converge to a point (normally the camera’s image sensor). The longer the focal length of the lens, the narrower the field of view (FoV) will be.

The FoV can be classified into three types:

  • Normal view: offering the same field of view as the human eye.
  • Telephoto: a narrower field of view, providing, in general, finer details than a human eye can deliver. A telephoto lens is used when the surveillance object is either small or located far away from the camera. A telephoto lens generally has less light gathering capability than a normal lens.
  • Wide angle: a larger field of view with less detail than in normal view. A wide-angle lens generally provides good depth of field and fair, low-light performance. Wide-angle lenses sometimes produce geometrical distortions such as the "fish-eye" effect.

Figure 5. Different fields of view: wide-angle view (at left); normal view (middle); telephoto (at right).

It is always advisable to take a snapshot from the camera to verify the coverage is correct and the depth of field is sufficient to capture the requirements. As depth of field changes with the available lighting, make certain to verify this multiple times per day.


Axis product selector


To assist in the selection process, Axis Communications offers a
Product Selector Tool






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