For a successful installation, the selection of the correct camera is essential. There are a lot of factors to take into consideration: the coverage area and the viewing angle, the operational requirements (detection/recognition/identification), environmental constraints, and more. If the camera is to be used in harsh conditions, in very dark environments, or in environments with high levels of contrast, this must also be taken into account.
Guide to selecting a network camera:
1. Define the surveillance goal: overview or high detail
Overview images give a general view of the scene, or the general movements of people. Images with high detail are important for the 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 decision will aid in the selection of cameras, housings, and mounts, to make the installation discreet or more obvious.
3. Coverage area
For a given location, you should determine the number of areas of interest, how much of these areas should be covered, and whether or not the areas are located relatively close to each other. These parameters will determine the types of cameras required and how many.
Coverage of an area can be achieved by using multiple fixed cameras, or alternatively with just a few PTZ cameras. A PTZ camera has optical zoom capabilities that can provide highly detailed images, and it is also capable of monitoring a large area. However, even though a PTZ camera can pan a full 360o to anywhere in the area, it can still only provide a view of one part of the scenes at a time, whilst a fixed camera will be able to provide full coverage of its area all of the time. The full capabilities of a PTZ camera are best used by having operational staff monitor the video stream live, or by setting up an automatic guard tour.
Also available from Axis are panoramic cameras, which provide a 360o field of view, making them ideal for applications that require wide area coverage in a single view. These cameras can be used to detect activities in a large area and track the flow of people, for example in a retail store.
Another benefit that network video brings to the video surveillance market is the ability to move beyond the limitations of PAL/NTSC resolutions and frame rates, and to instead experience high-resolution video with excellent image detail. Cameras with different resolutions have different application areas and benefits. For example, for two relatively small areas of interest that are close to each other, a single megapixel or HDTV camera with a wide-angle lens could be used to cover both areas, instead of using two non-megapixel cameras for the same task.
4. Light sensitivity and lighting requirements
Outdoor environments require the use of a camera with an auto-iris lens, such as a DC-iris or P-iris. You might also consider the use of day/night cameras for their excellent light sensitivity. Are you going to need additional white lights, or do you need IR lighting? Keep in mind that because there is no industry standard for measuring light sensitivity, lux specifications for different brands of network cameras cannot be compared directly with each other.
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 clearly is a priority, it is important that the camera uses progressive scan technology.
For applications that require detailed images, megapixel or HDTV cameras may be the best option.
The most important video compression standard used by Axis network video products is H.264, along with Zipstream – Axis’ own, more efficient implementation of H.264. This offers the greatest savings in bandwidth and storage. Axis network video products also have support for Motion JPEG.
Many Axis network cameras have audio support, with a built-in microphone and/or an input for an external microphone, as well as a speaker or a line out socket for external speakers.
9. Event management and intelligent video
Event management functionality is often configured using video management software, and is supported by the input/output ports and intelligent video features in a network camera or video encoder. Making recordings based on triggers from the camera’s input ports or intelligent video functions provides savings in bandwidth and storage. This also allows operators to handle more cameras, as cameras with triggered recordings will not require live monitoring unless an alarm/event occurs.
10. Networking functionality
Things to consider include PoE, HTTPS encryption for encrypting video streams sent over the network, IP address filtering to allow or deny access, IEEE 802.1X to control access to a network, IPv6, and wireless functionality.
11. Open interface and application software
A network video product with an open interface provides 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 enables 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 Application Development Partners.
Another important consideration, apart from the network camera itself, is the choice of network video product vendor. As 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 range of network video products and accessories to meet both current and future needs. The vendor should also provide innovation, support, upgrades and long term product plans.
Once a camera has been decided on, it is a good idea to purchase and test a single unit before ordering larger quantities.
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.
It is always advisable to save a snapshot from the camera, to verify that the coverage is correct and the depth of field is sufficient for requirements. As the depth of field changes with the available lighting, make certain to verify this several times over the course of a day.
To assist in the selection process, Axis Communications offers a Product Selector Tool