Types and choice of security cameras (I)

By: Mark S. Wilson*

No matter the type of video, transmission, storage and handling software, no matter what kind of application is from the aisle of a school to the baggage reception of an airport, the heart of the system rests at the end. It's the camera.

Of course, there are digital and analog cameras. But there are more commonalities than differences between them. In the first of a series of detailed technical reports from Infinova, also available on the firm's website, the dilemma of when to move to ip was explored with a simple basic reason — jump based on cost control that prolongs the life of existing equipment. For most sites, migration will occur gradually, and during the process, IP and analog solutions will coexist, in some cases for many years.

As before, let's follow security director Terry Jones and Helen Smith, second in the management, who work for a medium-sized company, as they now face the decisions and complexities that come with the selection of cameras.

Types of cameras
Basically there are two general types of cameras: fixed and PTZ (pan, tilt and zoom). There are also two types of camera technologies: analog and IP or network cameras. Fixed cameras are not as complicated as PTZ models, which, on the one hand, can simplify the selection process as well as migration. On the other hand, since fixed cameras have fewer features and settings, it's crucial to have or buy the right lens for a specific application with them.

Most installations use fixed cameras and PTZ, depending on the needs. On average, PTZ cameras cost more than fixed ones. And since PDZs are generally larger than fixed ones, the latter can appeal to end users looking for aesthetics and security. For example, there are minidome fixed cameras, measuring only a few inches in diameter, for installations where appearance is an important consideration. Compared to traditional fixed cameras, the dome adds a level of extra shock protection and cleaning staff.

If a camera is outdoor, there are many options. One is the use of one of the so-called day/night units. When the camera detects that it is night, it increases the sensitivity. And it changes to monochromatic. Another option focuses on thermal imaging, night vision and infrared cameras. Often this alternative includes infrared lighting, which is achieved by LEDs installed inside the housing. When selecting IR Lighting, a general criterion of architecture and engineering people is one foot (30 cm) per LED. The downside: If something gets too close to the camera, it can create a flash in the image.

Megapixels and high definition
Compared to standard-definition cameras, megapixel and high-definition (HD) IP cameras are appearing— the brandy and cognac of cameras. Not all megapixel cameras are HD, but all HD cameras are megapixels. HD cameras are megapixel cameras but they also meet high definition television (HDTV) standards. As with much of the security camera industry, it all depends on the pixels—the number of pixels in this case.

At the beginning of the twenty-first century, there was a changing of the guard in the electronics industry. Standard definition, which had been the de facto technology for many decades, was joined by high definition. Standard definition (SD) refers to the digital video signal at 640 x 480 or 704 x 480 lines of resolution.

Very high megapixel cameras – 7, 10 and 14 – are designed for special applications and are intended for general surveillance activities. They require more bandwidth and more storage capacity, and higher resolutions often don't work at high frame rates, 1-2 frames/sec.

Advantages beyond analog
However, increasing detail or the "monitoring" area over the capabilities of analog technology is an advantage. The large image format allows the camera to capture greater detail or offer a wider field of view. Megapixel IP video consists of digital data that takes up bandwidth, so bandwidth control is essential in the design of a cost-effective IP video system. However, most IP cameras have built-in bandwidth control.

There are also diminishing returns when viewing images from megapixel cameras on most monitors. The maximum resolution of the monitor is what you see from the cameras. So with megapixel cameras the higher resolutions look the same. The real benefit of resolution with higher megapixels is in the use of digital zoom.

Sweep
Cameras may also vary by type of sweep. IP cameras use progressive or non-interlaced scanning in which all the lines of each frame are drawn in sequence. In contrast, analog cameras use interlacing in which only the odd lines are drawn alternately and then the even lines of each frame (each image is now called a field).

Returning to the need for coexistence of analog and digital cameras, Terry has already come to an important conclusion. Although in the past there were legitimate questions about the quality of the digital image that was produced, today IP cameras offer a higher image quality than analog cameras. One reason for this is the progressive sweep; end users gain a very sharp image when they watch a video for one frame at a time.

Advantages of progressive sweeping
- Higher vertical resolution than interlaced video with the same frame rate.
- Absence of visual artifacts associated with interlaced video of the same line speed, such as interline vibration.
- There is no need for intentional blurriness (sometimes called anti-aliasing) of the video to reduce interline vibration and eye strain.
- Offers better results for scaling to higher resolutions than equivalent interlaced video. Scaling works well with full frames, for that reason the interlaced video must be uninterlaced before scaling. De-locking can generate objects with a serious "comb effect".
- The paintings have no interlocking artifacts and can be used as still photos.

There are cameras that, as a camera package, the lens and motorized mechanism can do more things than the fixed versions. An example is panning, tilting, and zooming, or PTZ. There are countless situations in which the only viable option is a PTZ camera – analog or megapixel.

Pre-settings and quick movement through positions
An important factor that Terry and his colleague consider when selecting PTZ cameras is the number of predetermined positions that can be pre-programmed on the camera. Presets are a series of positions where a camera can be programmed to pass automatically over the course of a round, shift or day to ensure coverage of a specific area or when integrating a video surveillance system with an alarm or access control system. The camera can be programmed to move to a predetermined position when a certain event occurs, for example, when a door is opened.

How quickly the PTZ camera changes positions is another consideration. For example, a camera can move up to 280 degrees per second when moving to a predetermined position but up to 100 degrees per second when security personnel or a police officer control the device manually. Speed domes, which have the ability to move quickly through a series of positions, are an alternative, especially when there are many points to monitor with a single camera or if the threat is moving particularly fast.

Rotational speed is a strong feature of Infinova's PTZ domes, with 400 degrees per second between predetermined points. In addition, in default mode, positioning accuracy from one view to another is essential. Poor positioning produces a camera that does not signal the scene an operator selected to stop at the round. In relation to computer forensics, this can create useless evidence when suspicious activity needs to be reviewed. Infinova cameras have a predetermined accuracy of 0.1 degrees.

Zoom is another feature that Terry and Helen weigh, but a complicated consideration by the fact that many cameras have an optical zoom in addition to the digital zoom. An optical zoom makes distant objects appear closer using a series of adjustments to an optical lens. Many cameras also have digital zoom: instead of making a manual zoom through optics, an operator can increase the pixels. But there is a limit to the latter in terms of the blurriness of the visualizations.

Helen has a solid warning to her boss. Magnifying pixels doesn't help make surveillance images more usable. Digital zoom is only useful to the extent that it reveals dark pixels picked up by the camera. With megapixel cameras, they may pick up many more pixels than a standard security monitor can display, so that an operator sees the image at a lower resolution than the camera. In such a situation, digital zoom can add data to the monitor. But once again the digital zoom does not add more information; it just makes it blurrier.

Checklist for Managers
There are several questions that Terry and Helen decided needed answers when weighing their current and future use of cameras. Some can be answered thanks to the expert help of a systems integrator, architecture and engineering consultant or product manufacturer.

Among the principles:
- What do you want the cameras to see and what is the distance?
- What types of lenses are needed (wide-angle, normal, telephoto)? Can varifocal lenses be used?
- What resolution is needed for each camera?
- Are megapixel, high resolution or high definition cameras needed? What about thermals?
- Can the video control system accommodate the features of the cameras?
- Are licenses required for digital cameras?
- How many frames per second are needed for each camera?
- What is the total number of cameras required? Fixed or rotation-tilt-zoom (PTZ)?
- What types of cameras are needed: dome domes/mini-chambers?, bullet chambers?, compartments? PTZ?, installed on the wall or ceiling?
- If PTZ cameras are needed, are operators available or will PTZ be programmed based on an automated rotation pattern? Or will the PDZs be digital so that they can zoom in or move after a recording is made?
- Are the cameras in a special environment that requires compartments, such as explosion-proof housings?
- What kind of ceiling and walls are there (suspended ceiling, ceiling and solid walls, drywall)?

Among the areas to be covered:
- Are cameras needed outside?
- What areas do you want to cover outside (entrances, parking lots, open spaces, barbed wire)?
- Should the numbers be read on the license plates?
- Is there any lighting during the night? Are infrared illuminators, day/night or thermal cameras needed?
- Are dome cameras or camera compartments appropriate?
- Are heaters or fans needed due to weather conditions?
- What type of cable is required to lay from the cameras: coaxial, twisted pair, Cat 5e, fiber optic? Already installed?
- Can power over Ethernet (PoE) be used?
- Where are the electrical outlets located or will be located?

Note: The second part of this article can be found in our next edition.

* Mark Wilson is infinova's vice president of marketing.