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CMOS and CCD sensors explained

By: Andy J Thompson

The image sensor is the component which captures light and begins the process of turning it into a digital image. There are two types of security camera sensors: CCD (charge coupled device) and CMOS (complementary metal oxide semiconductor). Which of the two you choose depends on your application.

First a little background on each technology.

Wtih a CCD sensor, every individual pixel's charge is transferred through a single output node, which is then converted into an electrical signal. The signal is then sent as an analog signal. Because of the pixels can be devoted to light capture, and the image quality is usually pretty high.

With a CMOS sensor, every pixel performs its own charge-to-voltage conversion, and the sensor also performs amplification and noise-correction. The sensor also includes digitization circuits which allow the component to output information in a digital format. Because of the complexity of this design, the area devoted to light capture is reduced. And because each pixel must perform its own conversion, uniformity (image quality) is lower.

The production cost for both types of sensors are similar, but CMOS sensors sometimes require additional support chips to optimize image quality. CMOS sensors are great for devices that require speed and low power consumption, while CCD sensors excel in image quality and low light performance.

While both CMOS and CCD sensors have matured a great deal in recent years, when it comes to security cameras, I prefer CCD for outdoor applications and CMOS for indoor IP camera functions. Let me explain why.

In the still camera world, CCD and CMOS are almost identical in terms of performance. In fact, CMOS sensors are attractive in this space because of their much lower power requirements - an important feature for devices which run on batteries. In the security camera world, I find that CCD sensors outperform their CMOS counterparts in several key metrics.

The first and most important is light sensitivity. If you need a security camera with superior night vision capabilities, CCD is the way to go. The CMOS cameras I have tested, with or without IR illumination, were almost completely blind in the dark. Cameras with CCD sensors are very capable in low light applications, and are terrific when coupled with infrared illumination. If you need to record in low light situations, CCD is the way to go - do not even consider CMOS.

The second factor to consider is image quality. In the security camera world, while both technologies are getting closer, CCD still has the edge when it comes to image quality. This is because CCD sensors exhibit less image noise than their CMOS equivalents.

Why would one consider purchasing a security camera with a CMOS sensor? Mainly because these sensors are more prevalent in IP Security Cameras - that is, cameras that are equipped with built in web servers and communicate using the IP protocol over CAT5 cabling. These cameras tend to be very affordable and are great for indoor applications that require web based video streaming.

In conclusion, CCD sensors are the way to go for outdoor applications, low light scenarios or when a higher quality image is required. CMOS sensor based security cameras should only be considered for indoor applications with decent lighting conditions.

Article Source: http://articles.directorygold.com

Andy J Thompson is a freelance residential CCTV specialist from Canada. For additional CCTV tips and advice, you can visit his blog at www.securitycameratutor.com/

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