Why Image Quality Matters In Megapixel Cameras
The transition from analog to network video cameras changes the rules of image resolution.[IMAGE]2389501026-b51a7f9232.jpg[/IMAGE]
“Standard” network video (also known as VGA or Video Graphics Array, and roughly equivalent to what users were accustomed to with analog technology standards) is still the most common definition for network cameras, but higher resolutions are possible using today’s megapixel technology.
Megapixel literally means “one million pixels”, and more pixels mean more information in the image, providing more image detail. For example, a 1280×1024-pixel image (totaling 1,310,720 pixels, a so-called 1.3-megapixel image) has four times the resolution of a 640×480-pixel (VGA) image, totaling 307,200 pixels. Cameras with even higher numbers of pixels will soon become common.
Why Do I Need Megapixel Cameras?
Megapixel cameras provide the ability to cover a larger area with fewer cameras because of the detail of megapixel images. Such an application boosts the cost/benefit argument for megapixel cameras: Fewer cameras mean lower equipment expenses and lower installation costs.
The scope of a megapixel image area can also negate the need for traditional pan-tilt-zoom devices. Rather than moving a camera’s view to a specific area to see a detail, megapixel technology enables “virtual” panning, tilting and zooming to specific areas in a detailed image that covers a larger area, whether the image is being viewed live or from recorded memory.
Users can both view and record the broader image, and zero in to see specific details. Other applications for megapixel cameras include necessity of a more detailed image, for example to provide the ability to recognize a face or person in an image or to read a license plate. In gaming situations, systems are needed to capture the number or suit of a playing megapixel camera can capture important details in a point-of-sale surveillance application. Common among the various applications for megapixel technology is a need for superior image quality.
Megapixel Camera Technology
Megapixel cameras use one of two types of sensors, either a CCD (charge-coupled device) sensor or a CMOS (complimentary metal-oxide semiconductor) sensor, both of which convert light into electrons to create video images. CMOS sensors are less expensive than CCD sensors, use less power and are commonly used in digital cameras, camcorders and other consumer products, but tend to be more susceptible to noise. CCD sensors, familiar to anyone who has used an analog surveillance camera, create high-quality, low-noise images.
One advantage of CCD imaging over CMOS is low light capability; however, CMOS technology is improving in this area and will eventually be comparable (and less costly).
The image sensors are also various sizes. For example, recently introduced cameras from Panasonic use a 1/3-inch interline transfer CCD that performs in 1.3 megapixel or 3 megapixel mode. Progressive scanning ensures clear images with less motion blur and no “tearing”. The size of the image sensor, when combined with the number of pixels in a camera’s image, can affect the size of the pixels and thus the light sensitivity. Higher megapixel cameras inherently have poor low-light performance because more, smaller pixels mean that less light hits each pixel in the sensor.
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