The basic technology behind most surveillance cameras is the Charge Coupled Device (CCD). CCDs convert the images that come through the camera’s lens into electronic impulses. CCDs provide a good combination of low price and quality picture for security applications.
Camera formats are measured in inches: most surveillance cameras fall between 1/4" and 1”. This refers to the usable image size created inside the camera. For most security use, a small size is fine – 1/4" or 1/3” cameras dominate CCTV sales. Larger formats do not necessarily result in better images, but can be advantageous in dimly lit situations since they are able to gather more light.
Many newer surveillance cameras use digital signal processing (DSP) to convert the analog video stream to digital information, improving picture quality and to adding functionality. The DSP circuit in a camera can have a very large effect on the quality of the images.