Megapixel Density = Forensic Propensity

In the video surveillance world, most people are familiar with terms used to describe resolution–640 x 480 is VGA and 720 x 480 is D1 or NTSC, etc.  These numbers refer to the columns and lines of resolution (collectively pixel density), that compose the images produced with standard cameras. These images represent the level of detail that most industry professionals are typically working with.  When one tries to zoom in or enlarge images like these, the results are usually full of artifacts which appear as a blurry image. For forensic (i.e. criminal) investigations, such data is usually not of sufficient value because it does not provide enough pixels to discern the detail of a target of interest.

This is a long-standing problem for the video surveillance world and the reason why so many cameras fail to capture a readable image of a license plate or to reproduce identifiable features of a perpetrator’s face.

Now that the world is becoming increasingly familiar with high definition images via HDTV broadcasts viewed on flat screen televisions, people are becoming more familiar with the associated terminology: terms like “megapixel,” “1080P” and “high def.” Most people remember the first time they sat down to watch a ball game on a high definition TV. It was almost like looking out a window and directly watching the action that was taking place. The difference: pixel density.

One megapixel is one million pixels. Pixels are the individual “dots” of colors that compose the columns and lines we see on our monitoring screens. Today’s high definition television standards are 1280 x 720 and 1920 x 1080, approximately 0.9 and 2.1 megapixels respectively. The megapixel count on video surveillance cameras goes even higher. The higher the megapixel count, the higher the pixel density on the camera’s sensor. Compared to the typical analog or IP VGA surveillance camera which produces images of approximately 307,200 pixels or 0.3 megapixel, a five megapixel camera has more than 16 times the pixel density, providing 16 times more detail. This is extremely important when it comes to forensic analysis of an image.

Today’s image sensors are roughly half of the size of a postage stamp. The surface of that sensor contains all the pixels that are used to absorb the light. The more pixels, the greater the detail captured, enabling greater digital zooming, forensic inspection and use within video analytics. This is what allows megapixel cameras to zoom into distant details such as license plates, facial features and myriad significant objects.

For these reasons, megapixel video surveillance cameras are providing a revolutionary advancement in the security industry. Now the label on a package can be zoomed in and read from 15 feet away. A license plate can be seen clearly from 100 feet away. A face in a crowd can be identified from 200 feet away. The Department of Transportation number on a semi truck can be captured from 500 feet away and on and on. The possibilities are virtually endless with megapixel cameras.

Michael Hodor is the director of Sales-North America for Arecont Vision, Glendale, Calif.

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