High Definition TV Basics

Technologies and Resolutions

Resolution can be expressed in lines, but with digital technologies such as LCD, plasma and microdisplay televisions, it’s more common to measure resolution in pixels. Pixels are the tiny dots of colored light that act as the basic building blocks of a TV picture. Since pixels are organized in a grid pattern, the number of horizontal lines is equal to the number of pixels in a vertical line, and vice versa. Example: If there are 480 pixels running across the screen horizontally, the screen will have 480 vertical lines. Likewise, if there are 640 pixels stacked up vertically, the screen will have that number of horizontal lines.

Most HDTV formats are generally referred to by the number of vertical lines — and whether those lines are interlaced or progressively scanned — i.e., 480p, 1080i, etc. However, the number of horizontal pixels also matters. In general, the more pixels, the better the picture.

In practical terms, certain types of TVs tend to have certain resolution levels, as follows:

• CRT TVs – Analog CRTs (cathode ray tubes) don’t really divide their horizontal scan lines into pixels. For this reason, most CRT TV manufacturers won’t quote the true native resolution in their documentation. In general, CRT technology is capable of displaying HD-quality video. Some tube TVs can even display full 1080p resolution. However, the process by which the images are created is essentially analog, so making a realistic comparison between a CRT display and a truly digital technology  (such as plasma, LCD or  microdisplay projection TVs, for example) is difficult at best.
• LCD TVs –  Among digital TVs, flat-panel LCD (liquid crystal display) TVs come in the widest variety of screen resolutions. In fact, the U.S. retail marketplace currently offers 11 different LCD TV screen resolution varieties. The most abundant type – some 56% of all TVs offered for sale — is the 1366×768 variety, providing 720p HD capability with pixels to spare. There are 27 manufacturers who currently offer LCD TVs with native 1366×768 resolution at major U.S. retail chains (source: Current Analysis).

• Plasma TVs – These TVs run from 37 inches, up to more than 100 diagonal inches in specialty models. They also tend to be constrained to a much smaller, more manageable palette of screen resolutions. Partly, this is due to the fact that there are fewer manufacturers of the plasma screen component worldwide, so there tends to be greater standardization in screen size as well as resolution. While plasma TVs with 1080p (1920×1080 pixels) resolution are being manufactured in small quantities, none have yet been offered by U.S. retail electronics chains. As with LCD TVs, the most common screen resolution for plasma TVs is 1366×768.

Plasma TV Screen Resolutions:	HD/ED/SD
1366×768	HD (720p)
1365×768	HD (720p)
1280×768	HD (720p)
1024×1024	ED (480p)
1024×768	ED (480p)
1024×720	ED (480p)
640×480	ED (480p)
852×480	ED (480p)

• Rear Projection TVs (RPTVs) – Some RPTVs use CRT technology to generate their image displays, and so are subject to the same nebulous analog CRT resolution issues described above. All other RPTVs rely on a chip-based microdisplay technology, such as LCD, DLP or LCoS. LCD-base projection systemscontain small LCD panels. The miniscule pockets of liquid crystal material in the panels are constantly changing to allow or block light, turning pixels on and off to create the screen image. DLP originally stood for digital light processing, a technology created by chipmaker Texas Instruments. It uses processors with millions of tiny, pivoting mirrors that create pixels by aiming light onto or away from the screen. LCoS is a hybrid of both LCD and DLP, combining to best qualities of those display other microdisplay technologies (for more on LCoS, see “The Resurrection of LCoS”).

RPTV Screen Resolutions:	HD/ED/SD
1920×1080	HD (1080p)
1386×788	HD (720p)
1366×768	HD (720p)
1280×720	HD (720p)