On the other hand, if the goal is to identify persons and/or objects in a scene, cameras with higher resolution will be needed. For example, retail stores may need surveillance cameras for point-of-sale monitoring where managers can see every item a person is purchasing or to identify a face (see Image 3, at right). Managers have the option of using network cameras with telescopic lenses or lenses with zoom capabilities, or they can place the camera closer to the area being monitored. Retailers can also install megapixel network cameras, which will provide even higher resolution images that provide more details than non-megapixel cameras.
In either scenario, managers must follow best practices to ensure maximum security. It is important to note that a conventional CCTV camera providing 4CIF (Common Intermediate Format) resolution offers a resolution of 704x480 pixels (NTSC) or 704x576 pixels (PAL) after the signal has been digitized in a DVR or a video server. This equals a maximum of 400,000 pixels or 0.4 megapixels. For an overview image, 20 to 30 pixels are generally considered enough to represent one foot of a scene. For areas that require more detailed monitoring, the demands can rise to as much as 150 pixels per foot. For example, if a security team wants to be able to strongly identify people passing through an area that is seven feet wide and seven feet high, the camera needs to provide a resolution of 1,050x1,050 pixels, which is slightly more than 1 megapixel.
Other uses of megapixel technology
Megapixel technology can also be used in non-mechanical PTZ cameras. Conventional PTZ cameras have moving parts that enable users to pan, tilt and zoom to see one portion of the room at a time but not the entire scene at once. The wide angle non-mechanical PTZ using megapixel sensors shows the whole scene and lets the user pan, tilt and/or zoom to get more details, and does so without moving parts (see Image 4, at right).
By using the network camera in an overview setting, a security officer can zoom in on any suspicious behavior by just clicking on the part of the image where it is happening. No other PTZ camera can zoom in instantly on off-centered action. Plus, since there is no movement in the lens system, the camera instantly changes the field of view. Zooming will not decrease image quality and the lack of moving parts and users get a wide-angle lens combined with a three megapixel sensor.
When not to use megapixel technology
While megapixel network cameras provide clear benefits by way of image resolution and versatility, it is important to be aware of potential drawbacks with current megapixel technology. For manufacturing and cost reasons, many megapixel sensors are the same size or only slightly larger than sensors with less resolution. This means that each pixel is smaller in a megapixel network camera and consequently less light sensitive than a non-megapixel network camera.
In addition, since megapixel technology produces higher resolution video, it will increase demands on bandwidth and storage space. While bandwidth in modern networks is plentiful, storage will come at a cost and moving from VGA to 1.3 megapixel cameras will quadruple the storage cost at a given frame rate. Compression is important when using megapixel resolution cameras, and MPEG-4 can offer benefits here.
Many megapixel cameras have limited frame rate support while VGA resolution cameras for the most part support 30 fps (frame per second) and some even 45 fps or 60 fps. Many megapixel cameras only support 15 fps or less. For some applications this might be a limitation.
The Future of Megapixel
While VGA/CIF resolution cameras are the standard today, in a few years 1 and 2 megapixel cameras will be the standard. Additionally we can expect improved light sensitivity, higher resolutions and higher frame rates from megapixel cameras.
Higher resolution will make it possible to build even more advanced non-mechanical PTZ cameras, with higher coverage and zoom. This technology may eventually replace the most advanced PTZ dome network cameras of today - but not anytime soon. To cover 360 degrees and achieve 35x zoom a 500 megapixel sensor (yes, 500!) would be required, and that type of product is still many years out. Better compression such as H.264 will reduce some of the storage requirements and will accelerate megapixel deployments.
There is no question that the capabilities of megapixel technology will continue to significantly impact the network security market in addition to having a larger role in influencing mainstream buying behavior. The exciting part will be watching the technological advances unfold and adoption of IP-based technology increase, producing even more efficient and cost-effective systems.