Megapixel Has a Mega Future
In recent years, the new Big Thing at trade shows has been IP-enabled cameras. Now, a new Thing is here — the megapixel camera. Basically a high-definition, or extremely high resolution camera, the megapixel has taken the industry by storm, providing higher quality images than ever before. The impact of megapixel cameras is being felt throughout the marketplace. Let’s take a look at some of the basic concepts behind megapixel technology and an impact of a different type, the impact on the network.
Chips Are No Longer Down
A typical, standard resolution IP camera will produce images anywhere between 320 X 240 and 720 X 480 pixels, while some megapixel cameras offer resolutions of up to 4,872 X 3,248 (16 megapixel)! The extremely high-rate megapixel cameras are still very cost prohibitive, but cameras in the 1-, 2- and 5-megapixel range are beginning to match the price point of many standard resolution IP cameras. One method being used to achieve these high numbers is larger imager chips. During the past several years we have seen CCD (charged coupled device) imagers shrinking, from 1 inch to 2/3-inch to 1/4-inch and smaller. Megapixel technology is causing a return to larger chips, with the highest resolution cameras utilizing the same 35mm (1.3 inch) imager used in consumer and professional still cameras. The type of imager is also playing a distinct role in the megapixel marketplace.
CMOS Being Seen More
The CCD has been the king of the security camera industry for many years. Recently, the CMOS (complementary metal oxide semiconductor) imager has been making a real showing as megapixel cameras have taken off. As far as performance goes, both have their strengths and weaknesses, and both are used both in high-end, large megapixel products. The only real differentiator I have seen is that CCD cameras seem to have better low-light sensitivity than CMOS-equipped product. Some megapixel manufacturers are using CMOS imagers throughout their product line, such as Arecont Vision, while others, such as Avigilon, use CMOS for their entry-level cameras and large CCD imagers for their top-end lines.
Lenses Are Not Least
Another important thing to remember is that the correct lens is needed for the application. Standard off-the-shelf CCTV lenses may not be appropriate for megapixel use. The glass used in specially designed megapixel lenses must meet higher standards as any optical imperfections will show up more pronounced with extreme-resolution imagers. Some megapixel lenses still utilize standard CS type mounts, but if you are moving into the larger megapixel range and are using 22mm or 35mm imager cameras, special lens mounts will be needed. Often these larger imagers will use the same type of lenses available for 35mm still cameras. Lenses can still be varifocal or manual focal length, as well as manual or auto iris, depending on the camera and manufacturer.
New Calculation Variable To Use
The lens discussion brings up another good point. We’ve always had to do some minor calculations in order to pick the right lens, right? Well, we still do, but with an added wrinkle. Because the focal length of megapixel imagers can be so much greater than standard resolution cameras, we now have to add in the factor of pixel-per-foot (or meter) to correctly figure our imager/lens combination. Basically, this calculation will tell us, at a given resolution and distance, the number of pixels that make up 1 foot (or meter) of the scene. The more pixels per foot (or meter), the higher the amount of detail at that distance. For general surveillance and the ability to recognize an object or person, you would require about 40 pixels per foot. For forensic analysis or license plate recognition, you would want to get about 80 pixels per foot in your image. For extremely high detail such as facial recognition, you would need almost 120 pixels per foot. Achieving these high pixel-per-foot numbers may require a higher resolution camera or several megapixel cameras in a given area, depending on your needs. Fortunately, most megapixel camera manufacturers provide online calculators to help determine the needs and application.
Beware Of Network Nightmares
So now we’ve got cameras that can provide image quality far beyond anything we had imagined just a few years ago. There must be a downside, right? You betcha! Ever since the first IP camera hit the scene, we’ve been well aware that video files create very large amounts of network traffic. Most standard IP cameras produce data streams anywhere in the range of 240kbps up to 4 or 5Mbps. That’s nothing compared to some of the new megapixel cameras. It has always been important to design networks carefully when IP video is in the picture. It is even more important now. Remembering there are many different factors that determine network throughput (resolution, compression type, compression ratio, images per second), megapixel cameras can produce great amounts of traffic. One calculation I did shows a 2.1-megapixel camera, at 10 images per second, producing 21Mbps on the wire. In some cases, I’ve seen numbers up in the 40 and 50Mbps range. One important note here, megapixel cameras are generally not designed (and some not even capable of) for running at 30 ips as we have grown accustomed. The maximum most megapixel cameras run at is 10 to 20 ips, with the larger imagers down at 2 or 3 ips. However, the increased resolution and ability to zoom in and maintain a clear image far outweigh the lack of fluid video. Also, an entire system of megapixel cameras may not be practical either; 40Mbps on the network is a very large amount of video to store. Just as we have seen before, however, as storage capability grows and price shrinks, so will the applications for megapixel cameras.
MCSE- and CCNA-certified Steve Payne has 15 years of industry experience, presently serving as a network/security system sales engineer and trainer for Warren Associates. He can be reached at email@example.com
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