Night/Day Cameras and Auxiliary Infrared LED Illumination|
Article- October 2011 By Larson Electronics.com
Larson Electronics LED IR Illuminator Light
In this day and age of rising crime and the growing threat posed by terrorism, finding ways to provide some sense of security for our families, businesses and homes has become a serious concern for a fast growing number of the general public. In most parts of the country, gone are the days of leaving doors unlocked and windows open. It’s no longer reassurance enough to count on local law enforcement to be there when needed. Gun ownership, home security systems, automatic exterior lighting, high end door locks, and even specialized safe-rooms have all seen an explosion in interest and growth as a growing segment of the public looks for ways to combat crime and protect themselves.
When it comes to considering home and business security, two items immediately spring to mind; alarm systems and security cameras. Thanks to high demand and easily available technology, these security systems are no longer the sole domain of big businesses or the well off, and are easily within reach for the average homeowner. Go to almost any department store and it’s a safe bet you’ll be able to find at least one of these security devices sitting on the shelves, if not several different makes and models of each. These days, the average homeowner or small business has available to them the ability to easily monitor and record all activity that takes place on their property. While this is generally a good thing, it’s important to note that not all security systems are created equal, and a wide variance in designs and quality means the consumer must be wary and informed if he is to make an effective choice of systems.
The average security camera systems purchased by most cost conscious homeowners are bargain value camera/recorders consisting of a set of three or four day/night analog CMOS cameras and a digital recording receiver. Usually priced around $150.00 to $250.00, these systems are indeed affordable, but offer a very a limited degree of effectiveness. While these systems are effective for showing you any activity that may be taking place within the systems range of coverage, you will likely not be able to capture detailed images or video with enough resolution to make definitive identifications of facial features or license plate numbers. This sort of system may indeed be sufficient for many, but to get the most effectiveness from a camera system it is better to pay a little bit more for higher quality. After all, once you’ve been burglarized, the camera is only worth the quality of the images it has captured.
Exacerbating issues with picture quality is the critically important proper installation of a system. Most people are not well versed in camera types, their strengths, and their weaknesses, and how to properly install a system to get the highest level of performance possible. A poor camera system that has been properly installed and operated will outperform an improperly installed system any day depending on the degree of error. For instance, a basic day/night SMA camera will capture a decent image if properly placed and augmented with an infrared light source, while a dedicated night vision system placed in an area of total darkness will produce nothing but dark and grainy images. Thus, what we’d like to focus on a bit here is camera types and getting the most out of your system, and hopefully leave you with a better idea of what to look for and how you can maximize the performance of any system you decide to purchase.
There are two dominant types of security cameras in use today; analog CCTV and Internet Protocol cameras. Analog cameras are by far the most common and what you usually find in bargain security camera systems. These cameras produce an analog video signal that can be played directly on a television or recorded by standard VCR’s and video recording systems. You cannot simply connect an Analog security system camera to a PC and begin managing videos and images. To store image and video data digitally, a DVR is required that can take the data and process it into digital form, which the DVR then stores on an internal hard drive. Power for these cameras is usually 12 volts DC and provided by a separate transformer either contained within the included recording system or connected externally. As you can imagine, these are usually fairly cheap systems and limited in what they can do. You won’t get a lot of camera control or high resolution image quality with these systems.
Internet Protocol cameras offer a great deal better performance than analog cameras, typically with a host of various built in features such as the ability to process and store images and video internally to memory or removable storage cards, and send and receive data over networks or the internet. There are two kinds of IP cameras, centralized IP cameras which need a separate recording system in order to manage and store data, and decentralized IP cameras, which can handle all image processing autonomously and store the image and video data internally on their own hard drive. All IP cameras, however, can be connected to a network and/or the internet in order to form a comprehensive video monitoring system that can be remotely accessed, controlled, and used to download video data to any location through a computer browser.
These cameras are usually of a higher quality than analog cameras and produce images and video with far greater resolution. This level of performance does come with a higher price, however, but the ability to capture detailed images of a quality good enough for positive facial recognition alone can make the added expense worth the cost. There are other benefits as well which further help to justify their higher cost. For instance, since these IP cameras can process their own data and create readable image data that can be played or stored directly onto on any reading device or PC, the recording source can be a DVR or a normal PC. All the image processing is done at the camera, so it is only necessary to store the data, thus a PC can be set up to handle all the recording and storage duties if desired without increasing the processor load on the PC. Also, the connecting cable for an IP camera is the same as the ones used to connect computers to modems and network adapters, making the creation of several cameras networked together onto one PC simpler.
Both forms of cameras require some careful consideration as to placement and whether or not added illumination is going to be required. Analog cameras, because they are more simply a camera and little else and thus have less internal hardware, can be made quite small and used in covert applications where you’d prefer the camera remain hidden. IP cameras are generally larger and heavier, and thus harder to conceal. With either type of camera, it is critical that considerable thought be given to placement. For example, cameras should not be placed near exterior lamps because of the tendency for insects to congregate near them. All it takes is one spider to set up shop over the camera lens and image quality will be ruined, requiring frequent cleaning to maintain a clear view. Additionally, light sources should be kept well out of the cameras’ field of view in order to avoid the overexposure and glare that light shining directly on the lens can cause. If you are concerned with obtaining clear images of facial features, keep in mind that a camera mounted at a high level is easy to defeat by simply wearing a hat or hooded sweatshirt or coat. When setting up a camera, take into consideration whether or not the locations you are considering offers a clear and unobstructed field of view. If you wish to obtain details like facial features or license plate numbers, work to keep the camera height at a level that will allow as direct a view as possible without putting the camera within easy reach.
Night Vision Cameras:
Day/Night cameras require some additional thought. Although a camera may be marketed as low light capable or having “night vision” capability, not all day/night cameras are the same. In both analog and IP cameras noted as having day/night capability, it’s possible that one of two types of adaptations for low light conditions have been used.
ICR (Infrared Cut- Removable):
Most modern cameras have internal CCD or CMOS sensors that are sensitive to light over a wide spectrum. Not only do these cameras register visible light, but light in the invisible infrared range as well. This means that these cameras can be used to capture excellent daytime images and video as well as good quality images and video in total darkness if so desired. In cameras designed for day/night applications, a special filter blocks infrared light during the day to allow the best possible image capture with normal lighting. At night, this filter automatically switches to allow any available infrared light in, thus providing additional light energy that can be used to produce an image. This is what’s known as an ICR filter and cameras equipped ICR filters tend to produce images of higher quality in both daytime and nighttime conditions. When paired with an infrared light source, these cameras can produce efective video even in total darkness.
DSS (Digital Slow Shutter):
Digital slow shutters accomplish night vision through an entirely different means. Rather than use a sensor that is sensitive to light across a broad spectrum, DSS cameras simply increase the exposure time, thus allowing the camera to gather more light and form a brighter image. These are poor cameras for surveillance as they cannot film motion well at all. For static snapshot images, these cameras can do well, but the long exposure time makes anything that moves during filming appears as nothing more than bright streaks and blurred shapes. Obviously, for day/night security applications, avoid DSS cameras.
Supplemental IR Lighting:
Many cameras now come equipped with a ring of infrared LEDs around the lens in order to provide an additional invisible light source that the bad guys can’t see, but the camera can see just fine. These infrared lights are automatically switched on when the available lighting drops below a certain level, typically at sunset, and produce enough infrared light for the camera to continue taking footage, even in total darkness. By circling the LEDs around the lens, the infrared light is always perfectly directed towards wherever the camera is aimed. This is an effective arrangement, but it should be kept in mind that these auxiliary infrared LEDs are limited in power and produce a short effective range. Additionally, images and video taken with night mode lack color and do lose some detail because the infrared light is a narrow band of the light spectrum and does not reflect colors, and so some image data is lost.
To greatly improve the effective range of an ICR equipped camera as well as improve image quality during night mode, many users include an external infrared light source. This is usually a compact infrared LED light bar that is mounted atop the camera itself, or attached to the same mounting bracket as the camera in order to keep the light constantly directed on the area being monitored. Although we cannot see infrared light, it is still light, and the camera registers it the same way we would were the light visible. Thus, adding more infrared light increases illumination, thereby increasing the effective range of the camera and improving its resolution. When adding an external IR source, keep in mind that just as with visible light, you do not want the light to shine directly into the camera’s field of view. As we mentioned earlier with mounting cameras near lamps, allowing a strong light source, infrared or visible, to shine directly into the cameras lens can cause overexposure and whiting out of the image. Also consider using an IR floodlight and not the IR spotlights. IR floodlights illuminate a much wider area with a more diffused light pattern while IR spotlights create an intense hotspot that can cause overexposure and whiting out in the center of the image.
On a final note, when considering the purchase of a day/night security camera, look for ones with the lowest nighttime lux ratings. Although it’s not always the case that the lowest lux rating will mean the best nighttime performance, its true enough to seriously consider. Also, if you need to add additional lenses to your cameras, be sure to purchase units which allow IR light to pass unhindered. Some lenses may actually block the passage of IR light into the camera, and thus degrade the quality of images taken in low light conditions.