Friday, December 21, 2007

Understanding HDTV Resolution

What the numbers mean, and what really matters

If you're shopping for an HDTV, you've probably seen terms like "720p" and "1080p", or "1366 x 768 pixels" used to describe a television's resolution. But what exactly do those numbers mean, and what do they say about a TV's performance? In this article, we'll walk you through the basics of resolution, and give you some practical tips to help you decide how high a resolution you need for your new HDTV.

What is resolution?

The main reason high-definition TV pictures look so much sharper and clearer than regular TV is HDTV's higher resolution. In today's world of digital TVs, resolution is measured in pixels, with more pixels providing higher resolution. Old-fashioned TVs had the equivalent of around 300,000 pixels, while today's HDTVs offer one to two million — up to six times more. All those additional pixels mean a huge jump in picture quality.

Side-by-side comparison of two versions of the same image, with different resolutions

The image on the left simulates the picture resolution of an old-fashioned TV, while the image on the right simulates high-definition TV. Notice the soft edges and jagged lines in the non-HD image.

When we talk about picture resolution, we're actually talking about two things: the resolution of your TV's screen and the resolution of the video source (your DVD player, cable box, etc.). Both are important, and each can affect the other in determining the quality of the picture you see. Let's take a closer look at each so you know how they relate, and how to get a good high-resolution picture.

TV screen resolution

Nearly all of today's HDTVs are "fixed-pixel displays," meaning their screens use a fixed number of pixels to produce a picture. That includes flat-panel LCD and plasma TVs, as well as front- and rear-projection types that use DLP, LCD, or LCoS technology.

All of these fixed-pixel displays have a native resolution that tells you the maximum level of image detail a TV can produce. Two of the most common resolutions are 768p and 1080p, though you may also see 720p.

You may see these same resolutions listed as "1366 x 768 pixels" or "1920 x 1080 pixels." That tells you precisely how many pixels the screen actually has: the first number is the horizontal resolution and the second number is the vertical resolution. Multiplying these two numbers gives you a screen's total pixel count. As an example, 1920 x 1080 = 2,073,600 pixels, which is usually simplified to "2 million." By comparison, 1366 x 768 = 1,049,088 pixels — slightly over one million.

Comparison of three common screen resolutions

These grids simulate the different-sized pixels of common TV screen resolutions, from 480i (the resolution of old-fashioned TVs) to high-definition 720p and 1080p. As resolution increases, the pixels get smaller, allowing much finer picture detail to be accurately displayed.

Now, let's move on to video source resolution. Then, we'll explain what "i" and "p" mean when you see one of those letters next to a resolution number.

No comments: