The Great Megapixel Debate

Your personal digital camera gives you a six megapixel image. Your teenage daughter’s cell phone captures two megapixel photos. Why are you satisfied that the camera in your surveillance system is limited to 0.3 megapixels (at 4CIF)? Chances are...


Reducing the number of cameras
Paul Bodell, vice president of Sales and Marketing at IQinvision called the bandwidth problem a “myth” because it’s usually not viewed in the proper context. Bodell said that it’s wrong to compare the data rate of a single megapixel camera with a standard-resolution camera.

The value proposition for many megapixel camera purchases is the reduction of the number of cameras required to provide surveillance coverage. Megapixel cameras can cover a much larger viewing area versus NTSC resolution cameras, reducing the total camera and installation cost of a surveillance system. Bodell surmised that in some situations a 1.3 megapixel camera could replace six or seven analog cameras while providing equivalent coverage.
The most common applications are outdoor spaces (parking lots, public transportation areas) that involve wide areas. Bodel estimated that over 80 percent of IQinvision cameras are used in outdoor applications. IQinvision has over 19 camera products, many of which are designed for outdoor use. Models include mini domes, all-weather systems and cameras with day/night capabilities.

In addition to camera reduction and overall better video quality, Dave Tynan, vice president of Sales and Marketing at Avigilon noted that a megapixel camera system offers improved situational awareness. “With conventional surveillance systems and pan-tilt-zoom cameras, security professionals have to make a choice between seeing the whole parking lot, situational awareness, or a single license plate-- the detail. But they can’t see both at the same time.” After an incident, if the PTZ camera was not positioned on the right detail, the incident is not recorded. With digital PTZ, the megapixel system is able to deliver both situation awareness and detail at the same time.
Unlike a traditional PTZ camera that ignores the bigger scene while in a zoom mode, the megapixel system can continue to provide live images of the full scene while providing a zoom image of a detail. Likewise, the digital PTZ features can be used in playback mode to provide a close forensic review of an incident without sacrificing quality.

Tools for surveillance design
IQinvision and Avigilon as well as others provide installers with calculator tools to determine how many cameras are needed to adequately cover a given horizontal area at a desired video quality. The idea is to apply the required number of pixels to the application. For example, to reliably recognize a license plate requires 50 pixels per foot whereas a face requires 90 pixels. IQinvision’s calculator helps the installer calculate how many frames per second should be captured to match the speed of an object (car versus people).

Tom Galvin of NetVideo Consulting is a network video specialist. His Web site is www.netvideoconsulting.com.