Anamorphic widescreen can refer to either a technique of motion picture cinematography that captures a widescreen image on standard 35mm film, or a similar principle applied to DVD recordings to allow for the best picture quality possible. In either case, anamorphic widescreen involves the compressing or “squeezing” of a widescreen image to maximize resolution.
PAL and NTSC
The United States favors a format called NTSC, which is short for National Television Standards Committee, while Europe, Australia and parts of Asia use a competing format called PAL, or Phase Alternating Line.
The differences start with the electrical power system behind the transmissions. In the United States and other countries, electrical power is generated at 60 hertz, so for technical reasons the NTSC signal is also sent out at 60 ‘fields’ per second. Since most televisions use an interlaced system, this means that 30 lines of the image are sent out, followed by the alternating 30 lines. This line alternation happens so fast that it becomes undetectable, much like a film running through a projector. The result for an NTSC television is 30 frames of a complete image appearing every second.
Europe uses a 50 hertz power supppy, the equivalent PAL lines go out at 50 fields per second, or 25 alternating lines. PAL televisions only produce 25 complete frames per second, which can cause some problems with the proper display of motion. Think of it as the ‘silent movie effect’, in which the actors seem to move a little faster because there are fewer frames showing movement. If a PAL movie is converted to an NTSC tape, 5 extra frames must be added per second or the action might seem jerky. The opposite is true for an NTSC movie converted to PAL. Five frames must be removed per second or the action may seem unnaturally slow.
another difference in NTSC and PAL formats is resolution quality. PAL may have fewer frames per second, but it also has more lines than NTSC. PAL television broadcasts contain 625 lines of resolution, compared to NTSC’s 525. More lines usually means more visual information, which equals better picture quality and resolution. Whenever an NTSC videotape is converted to PAL, black bars are often used to compensate for the smaller screen aspect.
WIDESCREEN HIGH DEFINITION
The standard high-definition television resolutions fall into three categories: 720p, 1080p. and 1080i, where 1080p is often referred to as true or full high-definition (HD). These resolutions refer to the frame size of the image, where the number represents the number of vertical pixels in the image. In 720p, the actual resolution – horizontal x vertical – is 1280 x 720; in the 1080 resolutions, the frame size is 1920 x 1080.
ATSC standards call for a variety of DTV screen resolutions and picture aspect ratios, including standard definition (SD) broadcast in 480i/p and 576i/p with aspect ratios of 4:3 and 16:9. For ATSC HDTV, screen resolutions are defined under the three standard HD image sizes and scanning modes, and all HD broadcasts are in the 16:9 widescreen aspect ratio. Image frame rates, given in hertz (Hz), cover a broad range for HD signals. Frame rates for 720p range from 23.976 Hz up to 60 Hz, 1080i ranges from 25 Hz to 30 Hz, and 1080p from 23.976 Hz to 30 Hz.
A flat screen television is a type of television that is only a few inches thick and has a perfectly flat screen, not the slightly curved screen that was used on older CRT models. These are also referred to as flat panel televisions, and are available in LCD and plasma varieties. Flat panel displays refer to computer monitors in this flat screen design. A flat screen television is a very popular choice for many homes, due in large part to its traditionally excellent picture quality and wide range of options.
A liquid crystal display (LCD) is a thin, flat electronic visual display that uses the light modulating properties of liquid crystals (LCs). LCs do not emit light directly.
They are common in consumer devices such as video players, gaming devices, clocks, watches, calculators, and telephones. LCDs have displaced cathode ray tube (CRT) displays in most applications. They are usually more compact, lightweight, portable, less expensive, more reliable, and easier on the eyes. They are available in a wider range of screen sizes than CRT and plasma displays, and since they do not use phosphors, they cannot suffer image burn-in.
LCDs are more energy efficient and offer safer disposal than CRTs. Its low electrical power consumption enables it to be used in battery powered electronic equipment. It is an electronically-modulated optical device made up of any number of pixels filled with liquid crystals and arrayed in front of a light source (backlight) or reflector to produce images in colour or monochrome.
CRT stands for cathode ray tube, describing the technology inside an analog computer monitor or television set. A CRT monitor or TV is readily recognizable by its bulky form. LCD monitors and plasma television sets, or flat panel displays, use newer digital technologies.
The CRT monitor creates a picture out of many rows or lines of tiny colored dots. These are technically not the same thing as pixels, but the terms are often used interchangeably. The more lines of dots per inch, the higher and clearer the resolution. Therefore 1024 x 768 resolution will be sharper than 800 x 600 resolution because the former uses more lines creating a denser, more detailed picture. Higher resolutions are important for displaying the subtle detail of graphics. For text, resolution isn’t as critical.
WHAT IS THE DIFFERENCE BETWEEN SQUATRE PIXELS AND NON SQUARE PIXELS?
Pixels in the graphics world are square. A 100 pixel vertical line is the same length as a 100 pixel horizontal line on a graphics monitor.
Some pixels in the standard-def video world (specifically, the digital electrical signals universally used in studios for 480i and 576i production, as defined by the infamous ITU-R BT.601-4 or “Rec. 601”) are non-square. A 100 pixel vertical line may be longer or shorter than a 100 pixel horizontal line on a video monitor, depending on the video system.
The term which describes this squareness or non-squareness is pixel aspect ratio, expressed as a fraction of horizontal (x) pixel size divided by vertical (y) pixel size. The pixel aspect ratio for square pixels is 1/1.
The pixel aspect ratio of non-square pixels is:
You can think of these values as the ratio of the width of a pixel to the height of a pixel. For example, say you want to draw a circle that appears round on the display device and whose diameter is n horizontal pixels (luma sampling instants). Draw an ellipse which is n pixels wide and n*hSpacing/vSpacing pixels (picture lines) high. Notice that vSpacing is in the denominator: the greater the vertical spacing of pixels (picture lines), the fewer vertical pixels you need in order to match a given number of horizontal pixels (luma sampling instants) on the display device.