Screen Resolution and Aspect Ratio

Many people are familiar with the concept of screen resolution. Resolution is a measurement of how many individual pixels your TV or computer monitor can display at once. The old cathode ray TV (CRT) in your basement can display the equivalent of about 300,000 pixels [source: Kindig]. The latest HDTVs can display more than 2 million pixels. With more pixels, the image can be rendered in greater detail. It's the difference between painting a portrait with a thick sponge block or a small, delicate brush.

The standard way to classify TV resolution is with numbers like 480i, 720p, 1080i and 1080p. The bigger the number, the greater the screen resolution. The little "i" and "p" stand for interlaced and progressive scan. This has to do with the way in which the image is rendered on the screen. Refresh rates on TVs and computer monitors are measured in hertz. A refresh rate of 60 times per second translates to 60 hertz. An interlaced-scan TV refreshes half of the screen image 60 times per second. It refreshes the odd-numbered horizontal lines first and then the even-numbered lines. The result is that the full screen refreshes 30 times a second.

On a progressive scan television, the entire screen refreshes 60 times a second. The result is that progressive scan TVs have a noticeably smoother image when watching sports or other video with fast-moving action. All computer monitors are progressive scan [source: PCMag.com]. Some even have refresh rates faster than 60 times a second. This is why interlaced SDTVs make for lousy computer monitors. When you scroll, the image can't refresh fast enough to keep things smooth. As a result, you see that telltale flicker.

Resolution is important, but you must also take a screen's aspect ratio into account. Your goal when hooking your TV up as a monitor is to make the entire image fit within the boundaries of the TV screen. SDTVs use a 4:3 aspect ratio -- the ratio of the screen's width to its height is 4 to 3. HDTVs have a native 16:9 aspect ratio. While many computer monitors share those aspect ratios, not all of them do, and your computer may support many different screen resolutions with different aspect ratios.

In fact, your computer's preferences are unlikely to tell you the aspect ratio, and instead will tell you the resolution. The horizontal x vertical measurement is also the most common way to label computer monitor resolution. Some typical monitor resolutions are 640 x 480, 800 x 600 and 1024 x 768. If you don't know your monitor resolution, you can find out by going to whatismyscreenresolution.com. If you aren't connected to the Internet and you're using a Windows PC, right-click on the desktop and choose Preferences. Then choose the Settings tab. On a Mac, go to System Preferences and click Displays.

The trick is to find the resolution that best fits the TV's aspect ratio. This may not be as big a deal as it sounds, though. Modern operating systems can usually match the attached monitor's aspect ratio automatically. If your computer doesn't, you can manually adjust the settings in your computer's preferences to make it fit.

But there's more to hooking these two machines together than resolution and aspect ratio. You still have to get the information from the computer to the TV. In order to do that, we've got to solve the cable conundrum.