THE MAGAZINE

Decoding the Digital Picture

By Laura Spadanuta

Resolution

Resolution affects CCTV systems in several ways. The most direct relationship is that the higher the resolution, the better the picture quality. But there are implications to this simple statement, such as if the resolution is high enough, as with megapixel cameras, one camera may be able to do the job of several, because operators can digitally zoom in on specific quadrants without the picture becoming too pixilated (more on this later).

There are basically three camera options in the CCTV world:  analog cameras, nonmegapixel IP cameras (which, according to JVC security division engineering manager Adrian Parvulescu, refers to cameras that produce similar video quality to analog cameras but have an Ethernet connection and include a computer that encodes the video and can serve other IP functions), and megapixel cameras.

Analog cameras are restricted by the video standards in each country (for example, in the United States the cameras are covered by NTSC standards), while digital cameras are independent of those standards, which allows them to keep becoming more powerful. Thus, 4CIF, sometimes called full TV frame, is the maximum digital resolution (equivalent to 704 x 480) when analog signals are converted to digital. (CIF, which stands for common interchange format, is the digitized version of the television standard for resolution). You need 4CIF for good facial detail, but each level of CIF increases storage costs.

Digital cameras can far exceed 4CIF, going into the realm of megapixel cameras, where the horizontal by vertical resolution equals one million or more. Companies can now find from one, two, and three megapixels all the way up to the 21-megapixel camera called the SentryScope, by Spectrum San Diego, Inc.

Megapixel cameras offer the ability to zoom in for greater detail in wide areas. For example, in a parking lot shot, if an end user wanted to digitally zoom into a picture to get a license plate number, it would be more effective to do so with a megapixel camera because there is more detail in the picture. With megapixel cameras, “because of the wide screen abilities, you can actually replace about three standard resolution cameras,” Sarangan says.

Having only one camera from one vantage point might be too restrictive, however, notes Banerjee.

It should be noted that many cameras offer an optical zoom (not to be confused with a digital zoom), from a few times magnification all the way up to twenty and more than thirty times. Resolution is not an issue with optical zoom. Parvulescu points out, however, that when the field of view is that magnified, every movement is exaggerated and the picture could become useless if it is too shaky. To avoid this problem, the end user must make sure that there is an image stabilizer built into the camera.

No one can deny the image quality improvement on a surveillance camera with one, two, or more megapixels. However, resolution like that does not come cheap, and you’ll pay in more than just dollars: There are also bandwidth and storage costs with each megapixel. Megapixel cameras take up more bandwidth in part because they use JPEG compression rather than MPEG, notes Banerjee.

The amount of bandwidth needed is the issue during data transmission. Then there’s the question of storage. “Probably the largest issue is resolution versus disk space,” says Clark Cummings, CPP, security director of FirstBank. The higher the resolution, the clearer the picture but the greater the storage requirement.

A company has to weigh those competing considerations in light of its own needs. As with all other aspects of CCTV, the choice of resolution depends on the application. Not enough people understand this concept, says Bordes. “A camera viewing down a hallway will require standard resolution whereas a camera being used for quality control on a product line may require much higher resolution,” he says.

Analog cameras have a range of horizontal and vertical resolutions measured in TVL (television lines), where 640 x 480 might be considered high resolution. Bordes says standard resolution, which he defines as around 330 to 360 lines of resolution, tends to be adequate for video surveillance. He adds that most cameras come with a specific resolution setting, so you have to know your needs when you make the purchasing decision.

Opinion varies widely on the necessity of megapixels in the surveillance field. Many agree that when dealing with critical infrastructure and certain environments, such as chemical plants, resolution should not be compromised. But in other applications, that quality may not be as necessary. “You can get great clarity, but do you really need that for event monitoring?” asks Wilson.

Most end users do not choose the 4CIF option for their video. “This tells me that [nonmegapixel] CCTV cameras are good enough for almost everyone, and that megapixel cameras will see niche sales,” says Banerjee.

Vlado Damjanovski, editor of CCTV Focus magazine and author of the book CCTV Networking and Digital Technology, agrees that there might not be a rush to megapixels for most applications. “There is still plenty of room and life ahead for standard definition CCTV,” he says, adding, “if a good choice of cameras, lenses, and compression is made, the standard definition CCTV can be processed better and quicker (more images per second) than megapixel.” Damjanovski does see the market heading to high definition TV (HDTV) one day as that technology becomes ubiquitous.

One application that may justify or benefit from high-resolution cameras is intelligent video analytics. Experts in this field say that if the megapixels improve, so can their algorithms. Fredrik Nilsson of Axis Communications, for example, says that his company will pursue advanced recognition of objects after cameras get better. “With better megapixel cameras, it’s going to be easier, because with megapixels, you’re going to get more data to evaluate,” he says.

Vidient President Steve Goldberg gives the example of someone 500 yards away. “If you have a low resolution…digital camera, you’re only going to get one or two pixels that cover that person,” Goldberg says. “But if you had many, many pixels, you can actually see if that thing’s got a head and arms and legs at 500 yards away. It’s like having binoculars.”

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