Size Matters! How Big Should My New HDTV Be?

I can still remember growing up in a Chicago suburb in the late 1970s with our own version of home theater. To have the true theatrical experience, we sat about 2 feet from the television, giving us the illusion that the image on the screen was really large. Playing the video game Pong was like watching a tennis match, requiring our heads to turn back and forth. Looking back, this provided a valuable lesson today on how to determine the proper screen size. While new high definition resolutions are important, one must also consider viewing distance as a major part of the home entertainment equation.

In Support of a Larger TV
There are good reasons to believe that upgrading to a high definition television justifies a larger screen. Going from a standard definition television to a widescreen HDTV will require a 22% larger screen to support the broader image while maintaining the same viewable height. Additionally, the increased resolution from standard definition to high definition will allow an 84% larger screen to appear to have the same picture quality. These reasons, combined with dramatic price drops, contribute to the logic and feasibility of replacing that old 30” picture tube with a 50” high definition television. To readers who appreciate me mentioning this: you are welcome (you know who you are).

In the past, television sizes ranged from 19” to 30”. Today, the right size television lies somewhere between a postage stamp monitor and a billboard-sized screen that stretches from wall to wall. Does it make sense, however, to ask the salesperson at TVs ‘R’ Us for advice on screen size? The last time I did, the seller also mentioned their low rental rates on cranes to facilitate installation. What consumers really need is logical, third party guidance on defining the appropriate screen size. The proverbial retail fox will be more than happy to give advice on how to guard the henhouse. But the fox may end up using a toothpick to clean its teeth while we try to figure out how to remove the fireplace and make room for a mammoth television.

The “Eyes” Have It
To help determine the optimal screen size, one factor that we can consider is the capability of the human eye, called visual acuity. A person with 20/20 vision is able to distinguish lines on a screen separated by 1/60th of a degree. How much detail this person can see on a television depends on the resolution (display lines on the screen) and viewing distance. The greater the resolution, the more lines on the screen, and the more difficult it is to distinguish the individual lines. If you are able to actually see the individual lines on a TV screen, you may need to sit farther away, get a higher resolution screen, or both. It is my belief that you don’t want to be able to distinguish individual lines. This will ensure top picture quality perception.

Standard or enhanced definition televisions that have DVD-quality screens will have 480 lines of resolution, while high definition (HD) televisions have at least 720 lines. The premium HD televisions, called “Full HD” or “1080p”, will have 1080 lines of resolution. Although we will only be referencing television with “progressive scan” lines, keep in mind that there is an alternate resolution that uses something called “interlaced scan”. These screens only refresh half of the lines each pass and are inferior to a progressive scan screen. For our purposes, we can assume that the 1080i (interlaced scan) picture quality is closest to 720p quality (progressive scan).

Home Theater vs. Home Entertainment
Detection of individual lines is not all we need to consider. To truly mimic a theater, we may look at cinema standards such as those set forth by THX, a company that certifies theaters to ensure an optimal movie experience. They have recommendations for viewing angles, which determines how large a screen should be for a given viewing distance. These guidelines create a theater experience and should be taken with a grain of salt when considering home entertainment usage. In a movie theater, the entire focus is on the screen. This may not be the same goal within a family’s living room.

In the following chart, the range of data we discussed comes together. Resolution detection of the human eye is combined with professional cinema standards as well as some retailer/manufacturer guidelines. A "screen size data" spreadsheet showing background calculations may be accessed online. For a given viewing distance, the chart shows a range of recommended screen sizes and the highest resolution that may impact the viewer’s perception. The black areas show recommendations for a true home theater experience while the gray blocks show guidelines for more typical home entertainment applications. Although the topic merits a more in-depth discussion, it should be know that there is some debate as to whether 1080p is noticeable or worth the premium price tag. Also, there is currently almost no 1080p content available except for HD video games, HD DVD, and Blu-Ray players. For the budget conscious, a 720p or 1080i may be sufficient.

Ultimately, personal preference also needs to play a major role in determining the best screen size for your application. This is the main reason why we see a range of TV sizes for each viewing distance. You may not want a home theater television “swallowing” the majority of your living space. But then again, there are few better ways to get immersed in the viewing experience than wrapping yourself in a widescreen television. To go with a TV of this size, however, you’ll also need a tub of popcorn the size of a garbage can, a soda the size of a beach pail, gumdrops the size of golf balls, and a dentist with an opening next week. Happy viewing and chewing!

(click on chart to make larger)