The Truth Application Of PTZ Cameras
Though popular, PTZ cameras often create a false sense of security. They make for great demonstrations but are often underutilized or misused.
The use of PTZ cameras varies significantly. Offices and fast food restaurants rarely use PTZ cameras. However, the majority of cameras at shopping malls and public surveillance are PTZs. In general, PTZs are the standard choice for monitoring large public areas.
Here’s a short video demonstration on YouTube of using a PTZ camera in action.
Monitoring large areas: the PTZ camera can be pan, tilted and zoomed to cover hundreds of acres (a few square kilometers). This is not possible with fixed cameras which normally only cover a small area (few hundred square meters).
PTZs can be placed on tours (patterns) that move the camera in a predetermined way to capture areas of interest. For instance, over a 1 minute period, the camera can capture the front door, the gate to the parking lot and the fenceline. The tour can repeat indefinitely.
Operators can control PTZ cameras to track a suspect or respond to a security incident. The operator can zoom in to view and capture fine details like facial features or license plate. The operator can also follow a suspect across a large area.
Because PTZs can cover a wide area, this reduces the cost of coverage per given area.
People love PTZ demos. They are the closest thing the surveillance industry has to movie special effects (see the demo above). It makes people feel excited about the potential.
Service issues: Since PTZs are complex mechanical devices, they tend to have much more frequent service calls and shorter live spans (compared to fixed cameras).
High storage costs: Because PTZs move so frequently, their storage utilization tends to be 2 – 4x higher than a fixed camera with equivalent frame rate and resolution. Motion based recording cannot be used (or it has little savings since the camera continues to move). Plus, encoding motion requires higher bit rates to maintain image quality.
Poorer image quality: PTZ image quality is often poorer than fixed cameras, especially when zoomed in. This is likely a result of smaller chip sizes (1/4″ for PTZs vs 1/3″ inch in fixed cameras) and the much larger focal lengths in PTZs (over 50mm focal length is common for professional PTZs).
Mispositioning of PTZs is common. Operators routinely place (or leave) the PTZ in different positions. While this can be solved by using a ‘home’ functionality, many systems are not configured to use this properly.
Works Poorly over IP Networks: Controlling mechanical PTZs are very sensitive to latency. If the latency is more than a fraction of a second, controlling PTZs become very difficult. This is not an issue for traditional analog systems but a growing problem for IP video. Furthermore, network viewing often requires on screen PTZ controls which are much harder for an operator to use. These issues can be somewhat rectified by using USB joysticks and manufacturer optimizations to reduce latency. However, this is a frequent problem with IP networks.
Higher Per-Camera Cost: Whereas a fixed camera may cost $200 – $500, a PTZ camera with a 15x or greater zoom can cost $1,500 to $3,000. The cost increase is significant.
The demos are unreflective of most real applications. While it’s impressive to see a building a mile away, that ability rarely solves real security problems for users.
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