Anyone considering an IP camera surveillance system is faced with a dizzying array of letters. First off, there’s the obvious – IP. It stands for Internet Protocol which is part of the name of a protocol called TCP/IP. This actually stands for Transmission Control Protocol/ Internet Protocol. A network protocol is the set of rules and conventions that allow computers to communicate on a network. As part of the rules there is an IP address that allows each computer to be addressed on the network.
But how about HD, PoE, IR, PTZ? Does your application call for these features? First, let’s decode this alphabet soup of terms one at a time - in alphabetical order of course.
HD - High Definition
HD can be considered a subset of Megapixel. While megapixel refers to any resolution over 1,000,000 pixels, HD is used in the TV market and refers to specific standard resolutions of 720p or 1080p. But in HD, 720p is not the number of pixels but rather the number of vertical lines. This is a TV type of term and it gets confused with the pixel resolution. Standard old NTSC TV used 525 vertical lines. The new HD TV systems went to 720 lines (720p) and also 1080 lines (1080p).
The “p” actually stands for “progressive” as opposed to “interlaced”. In olden days, when we were watching The Mickey Mouse Club, our TV sets used 2 fields that were “interlaced”. Each field had vertical lines that were interlaced with the next field. Half the lines (262.5 lines) were sent in each field and they were seen 60 times per second. The fields were locked to the 60 Hz power line. Two fields make up one frame, so each frame ran at 30 frames/sec. The new progressive TV system provides all the lines at one time.
IP camera resolution is measured in total number of pixels (for example 3 megapixels) and also by the horizontal and vertical pixels (2058 x 1536), rather than lines of resolution.
IR – Infra Red
IP video cameras need light. Without the reflection of light from the desired scene there is nothing for sensors to capture. When we think of light do we think of energy? We should. Light is electromagnetic radiation, and its frequency or wavelength is what determines its color. The human eye is capable of seeing only a narrow range of wavelengths, basically from 400 nanometers (violet) to 700nm (red). Think of the rainbow. The rainbow is the refraction of pure or white light and human sight is limited to this spectrum.
IP cameras are capable of detecting a broader range of wavelengths than we can, allowing them to function not only in white but also in infra-red light. Infra-red light occurs at higher wavelengths than is visible to the human eye: 715-950nm. The presence of infra-red lighting makes night-time surveillance possible.
A Day/night camera is made with the capacity to adapt to both day and night lighting conditions. During the day it employs an IR-cut filter to prevent distortion of the image. At night the IR-cut filter is removed, giving it functionality in light as dim as 0.001lux. In extremely dim conditions, an IR illuminator can be used to provide near-infra-red light, setting better conditions for a high-quality video.
PoE – Power over Ethernet
PoE is a method of supplying electrical power through Ethernet data cables to devices that would otherwise need to be plugged into a power supply. Making use of the PoE feature keeps the number of necessary wires to a minimum, allowing for flexible installation while lowering both cost and downtime that would be involved with traditional wiring.
The basic piece of the puzzle that will allow this to work is the PoE injector (sometimes called a midspan). At one end is a power cord that plugs into a power supply. At the other end are two ports into which data cables connect: data & power out and data in. In this way, current is kept separate from the data signal so they do not interfere with each other.
If the device plugged into the Ethernet cable is compatible, the device will function properly. In order to insure compatibility, standards have been established. The most widely used standards are IEEE 802.3af-2003 and IEEE802.3af-2007. The standard power provided is 15.4 watts. For a larger network with multiple devices, Ethernet midspans are available with 4, 8, or more ports. There are also PoE injectors that provide higher power. These high power units can provide up to 25 to 60 Watts of power.
There are also network switches that include PoE. These switches make it very easy to connect devices that can be powered over Ethernet because you don’t require the additional PoE injector.
PTZ – Pan, Tilt, Zoom
Let’s start by pointing out what a PTZ camera is not. It is not a fixed network camera. As its name implies a fixed network camera is mounted to give one field of view (normal, telephoto, or wide-angle). The lens can be changed but not its intended direction of view.
A PTZ camera, on the other hand, can pan (move left and right), zoom (move in for a close view), or tilt (move up and down). It can be moved manually or programmed to move to a preset position. You can set 20 to more than 100 preset positions (depending on the camera model). Once programmed, an operator can go from one position to the next in a matter of seconds. All PTZ commands are sent over the same network cable used for video transmission. Some PTZ network cameras are made to be used in an auto-patrol mode and some can’t. The auto-patrol is used to step the camera through the list of preset positions. Less expensive PTZ cameras are not durable enough to be used in constant motion, but the more expensive versions can be used in this way. Some more sophisticated PTZ cameras allow you to set up the presets and then turn on the patrol mode and then do motion detection only when the camera is not moving. The Axis Q6032 is an example of a PTZ camera with sophisticated auto-patrol mode capability. It moves through the preprogrammed positions and then sends video to the computer when motion is detected in one of the positions. It doesn’t detect motion when the camera is moving between the presets.
In the past we have equated digital PTZ to optical and mechanical PTZ but this can confuse people. When you digitally zoom in on a part of the picture you lose resolution. For example of you have a picture that has 1000 x 800 resolution and you zoom in to ¼ of the picture you will see a picture that has 250 x 200 pixel resolution. If you use optical zoom, and the camera has 1000 x 800 resolution, and zoom in to ¼ of the view, the resolution of that small part is still 1000 x 800 pixels.
Digital zoom is helpful, especially if you record a large area and then later want to digitally zoom to a part of the view. It just has to be done with the understanding that you have to start with a lot of resolution to be able to digitally zoom. A 3 megapixel camera can zoom about 3 X to 4X
Not sure which features you need? Kintronics engineers will listen to your application needs and suggest a system. Call 800-431-1658 or visit us at http://www.kintronics.com http://www.kintronics.com/neteye/neteye.html
