Picture quality is a major factor in digital TVs.
Since its arrival, the digital age of television has provided an array of viewing options, from on-demand shows to interactive entertainment. The television choices themselves have also increased in number, and, in turn, have made selecting the right digital screen for the home a difficult decision. To simplify things, a majority of televisions can be placed into one of three categories.
HDTV
Of the three types of digital televisions, HDTV is at the top of the list. The most noticeable difference between HDTV and the others is the resolution, which is nearly double that of the next type down on the list. Digital resolution is measured by what are known as scan lines. The more scan lines available, the higher the quality of the picture. Most HDTVs are labeled either 1080 or 720, which refers to the number of scan lines on the screen. Also, nearly all HDTVs are widescreen, much like the screen in a movie theater. The picture size is often referred to as "aspect ratio," and programs filmed in widescreen have an aspect ratio of 16:9, as opposed to the old 4:3 ratio on older televisions.
EDTV
EDTV is the middle ground between the top-of-the-line digital televisions and the very basic digital models. The resolution of the EDTV is 480 scan lines, which is significantly lower than the typical HDTV but compatible with deinterlacing devices. These devices, of which the most common example is the progressive scan DVD player, are designed to enhance picture quality, especially for televisions with large displays. The result is a much brighter and clearer picture. EDTVs, like HDTVs, come with wide screens, and they can also display anything shot in a 16:9 aspect ratio in its intended format, which again enables large-sized EDTVs with a deinterlacting device to display a clean and smooth picture.
SDTV
SDTV is considered the lowest quality digital television available. Although any SDTV is a step up from most analog sets, the resolution is still only 480 scan lines at best. And, unlike the EDTV models, these TVs do not come with any type of hardware that will enhance the quality of the picture. Although the resolution is noticeably lower, the most obvious difference between SDTV and the other two choices is the fact that most are not widescreen. The screen on an SDTV is the old-fashioned box shape, which is only capable of displaying images in a 4:3 aspect. Widescreen movies and shows can still be seen on this screen, they are just automatically shrunken in size with black "letter boxes" at the top and bottom.
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