As the world’s first color TV broadcast standard, NTSC was developed by National Television System Committee in 1953. With an image size of 704x480 and up to 30 frames per second, NTSC is mainly adopted in the United States, Canada and Japan that uses 60Hz AC electricity.
NTSC signals can be displayed on a black-and-white TV because they contain luminance signals and color information. However, it has the disadvantages of phase distortion and unstable color.
1967 saw the development of a new color encoding standard for TV broadcasting in Germany, known as PAL, which was exclusively developed for the 50Hz AC electricity used in Europe. PAL has an image size of 704x576, with a full frame rate of 25 per second.
Since the phase of the color information in each line is reversed, PAL reduces color distortion problems.
D1 format, also known as SMPTE 259M, is a digital image format developed by SMPTE Engineering Committee in 1986, and is used in tape recorders. In the NTSC system, D1 has an image size of 720x480, with maximum 30 frames per second; in the PAL system, D1 image size is 720x576, with maximum 25 frames per second. D1 format is commonly used by analog cameras.
CIF (Common Intermediate Format), frequently used in video conferencing, appeared for the first time in the ITU-T H.261 recommendation in 1990. CIF image size is 352x288, equal to 1/4 of a PAL image. Its full frame rate is 30 frames per second, the same as NTSC.
VGA (Video Graphics Array) format was defined by IBM in 1987, with an image size of 640x480. Because a common standard for PCs and industrial monitors, VGA has been widely used in digital image devices. IBM has extended the VGA standard further into 1024x768 XGA (Extended Graphics Array) and 1600x1200 UGA (Ultra Graphics Array).
A megapixel network camera features a resolution at least three times larger than that of an analog CCTV camera.
A megapixel camera is mainly applied in occasions when accurate identification is needed such as vehicle license plate recognition or facial recognition for it can provide images with exceptional details. Because of its high number of pixels, a megapixel camera is also used in spacious areas such as parking lots or airports to provide images with a wide view.
The megapixel sensor has contributed to a new breed of non-mechanical PTZ cameras, known as digital PTZ cameras. The camera captures a megapixel image and delivers only a user-defined thumbnail to the monitor so that users can view different images by selecting on the monitor instead of physically moving the camera.