HDTV Resolutions

One of the most confusing aspects for many HDTV buyers is the various resolutions that these formats may support. Most HDTVs on the market today support some range of resolution from 480p to 1080i. What do these numbers mean? The number refers to the number of lines of horizontal resolution the screen is able to display. Generally speaking, the higher the resolution, the better the display will appear in terms of picture quality and crispness.

So, what does the p or i mean? You may see the various TV resolutions labeled as 480i, 720P, or 1080i. These refer to whether the picture is (p)rogressive or (i)nterlaced. Before HDTVs, all TV displays in the United States were of the Interlaced variety. What this basically means is that as the TV 'draws' the picture, it draws every other line, and then goes back and draws the lines it missed. In other words, it draws lines 1, 3, 5, 7, etc. and then after completing all odd numbered lines, it goes back to draw 2, 4, 6, 8, etc. Of course, this all happens amazing fast, fast enough that the human eye can not actually see these lines being drawn. However, Interlaced displays are often noted to have a bit of shimmering or flickering as a result. For most of us, since this is what we have spent our whole lives watching, it appears quite normal.

Progressive on the other hand draws the lines in order, and at a higher number of framers per second. In other words, it draws lines 1,2,3,4,5 and on down, and does so at a higher speed than an Interlaced display. As a result, the display is generally much cleaner and appears sharper. For many, once they have seen a Progressive picture, it is difficult to go back to interlaced.

The most common HDTV standards set by the ATSC are 720p (720 lines of horizontal resolution and progressive scan) and and 1080i (1080 lines of horizontal resolution and interlaced scan). 720p is also generally described as TVs being capable of 1024x720 pixel resolution (similar the resolution settings on your computer monitor), but individual HDTV sets may have actual different resolutions and still be able to support 720p. This is particularly true of Plasma TVs. The same goes for 1080i, which is described as 1920x1080 pixel resolution Note that 480p is generally not considered a HDTV resolution, but a DTV (digital television) or ETV (enhanced TV) resolution that allows you to view improved clarity from a DVD player that supports Progressive output.

There is a pretty sizable debate ranging within the audio/visual community on whether 720P or 1080i produces a higher quality image. 1080i has the advantage of having more lines of resolution, whereas 720p has the advantage of a progressive scan picture. The important thing to remember here is that both will be much better looking generally than a standard 480i (non-HDTV) signal, and that all TVs are able to receive, display and/or convert these different formats. So, you should not have any issues in viewing any HDTV formats with current generation TVs. Also, keep in mind that true HDTV signals are always in a widescreen (16:9 ratio) format, compared to standard broadcast televisions 4:3 ratio.

Continue to Basics of HDTV: Types of HDTV Sets