Appropriate Applications for Megapixel Cameras
Although megapixel cameras may not be necessary for all applications, there are many where their technology provides an undeniably superior solution. Features like greater detail and wider coverage make them ideal for identification and forensic purposes.
Welcome to Part III of the latest in SECURITY SALES & INTEGRATION‘s acclaimed “D.U.M.I.E.S.” series: “Megapixel Video for D.U.M.I.E.S.” Brought to you by Pelco, this four-part series has been designed to educate readers about megapixel cameras and video – the next phase of surveillance technology following the leap from digital to IP-based, or networked, CCTV systems.[IMAGE]dumies8-1.jpg[/IMAGE]
“D.U.M.I.E.S.” stands for dealers, users, managers, installers, engineers and salespeople. Recently, the megapixel revolution has begun to affect all of us in the industry.
First came the megapixel camera, then megapixel lenses and, of course, megapixel video recorders. Perhaps the megapixel thermos is next!
It’s for certain that this changing technology is on a very fast track, and a great deal of hype has surrounded the megapixel revolution. But what exactly is this so-called revolution all about? What is required to support megapixel systems and what are the main advantages of megapixel and IP cameras over analog cameras?
The answers lie in this series of articles, which cover the theoretical and practical technology and design theories required to intelligently sell, install or service megapixel solutions. This edition tackles applications for megapixel cameras.
Devil Is in the Detail Requirements
By now everyone has been inundated by the countless advertisements for incorporating megapixel technology.[IMAGE]dumies8-2.jpg[/IMAGE]
Not every application requires megapixel technology. There are many systems min which a standard analog output camera will work just as well.
Deciding where to use megapixel cameras will depend on your application. In most cases, using a hybrid design approach that mixes both analog, IP and megapixel cameras may make more sense for a wider range of surveillance needs. One of the starting points is determining the level of video surveillance detail necessary to achieve the desired results of the particular application.
The three levels are as follows:
1. General – Viewing or recording general information usually consists of activity or movement within a certain area.
The areas can be traffic in parking lots, customer flow within retail stores and unauthorized entry into selected areas, where recognition of objects such as license plates or faces is not necessary.
2. Identification – The ability to recognize a person’s face or read license plates. This design will require more camera locations, higher megapixel valued cameras, and higher pixel per foot design.
3. High Detail / Forensic – The ability to identify every detail within the scene, such as what is usually required in the gaming, banking and forensic marketplaces.
Now we come to a concept that is affected by many different variables.
That is the amount of pixels per foot each application requires. Presently there are no set figures or standards listing the value required for producing detail for general, identification or forensic use. However, many providers are making recommendations on the number of pixels per foot for each application.
The first thing to determine is how many pixels the camera you have selected has to work with. A 1.3-megapixel camera has a horizontal pixel count of 1,280 by 1,024 in the vertical direction.
This calculates to about a 13-foot scene width to produce a high (forensic) scene quality. Confused about how to derive ~13 feet? Since there are no set standards (at least at the time of this writing) the number of pixels per foot can be very subjective with many different opinions.
As we are well aware, the more pixels per foot, the better the scene’s detail. This is especially true if electronic zoom is incorporated into the overall design parameter. But how many pixels are sufficient to produce a quality image? In addition, how many cameras are needed to cover a given area, and how many images would be required to meet the surveillance needs of that particular deployment?
To help us work through this, five theoretical applications round out the bulk of this article.
However, before diving into them, there is something else to understand. Most promotion pertaining to megapixel cameras dwells almost exclusively on image quality alone. It is also important to be aware of the number of images per second (ips) a megapixel camera is capable of producing.
Real-time video is listed as 60 images per second (interlace scan) or 30 images (progressive scan) for the normal rate. Real motion video is listed as 15 images per second. Any image rate that is lower than 15 images per second will result in jerky movement on the display or in recorded information.
With present technology, many of the processors incorporated in megapixel surveillance cameras do not have the power to reproduce 30 or 60 ips when used in the maximum megapixel mode. This causes fewer images per second to be processed, which can result in poor detection with moving objects, blurred image quality and even loss of object identification.
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