The bigger the picture the better. You can only sit so close to an standard definition TV before the individual scan lines that create the image become visible. The closest distance you can sit without seeing these lines is the "optimal viewing range". This range gives you the largest picture possible from your TV, and brings you into the on-screen action much more. The proper placement of both distance and height allows you to get the most out of any TV.

HDTVs
HDTV's are the exception to the rule as their lines of resolution are less visible due to their high resolution display qualities. Most HDTVs have a line doubler that takes any source and makes it progressive, enabling you to sit much closer to the screen. Simply get your HDTV to take up as much of your peripheral vision as comfortably possible. Do this by setting up your seating so that you sit as close as your comfort level allows.

The bigggest issue with how close you can sit before seeing the lines of resolution or pixel lines is that there are multiple formats for HDTVs. 720p HDTVs do not have as much resolution as 1080i HDTVs so you may not be able to sit as close to them. EDTVs (480p) may require you to sit even farther away.

With HDTVs start with a measurement of 2 times away the screen size. With a 65 inch screen the closest you could sit without seeing the actual image stracture is 130 inches or 10.8 feet. For a 42 inch HD plasma that's 7 feet away. It's not a hard rule, but merely a good place to start. Depending on the TV you may be able to sit closer.

Non-HDTVs (Size Matters Not)
Whether you have a mammoth direct-view set or a huge projection system you'll need to sit in the optimal viewing range so you don't see the lines of resolution. This means that by sitting in the optimal viewing range, whether you have a 48" or 27" TV, both TVs will take up the same amount of proportional space in your field of view when you sit in the optimal viewing range. The only difference is the comfort level that comes with having more space between you and your TV. The optimal viewing range of a 27" TV is 6 feet away while a 48" TV allows you to sit 10 feet away.

A larger set doesn't give a bigger picture. It just allows you to sit further away.

Just The Right Distance
To find the optimal viewing range of your TV, simply take the size of your TV screen (27", 32", etc.) and multiply by 2.5. That is the number in inches of how close you can sit in front of your TV without seeing the lines of resolution.

Only use this measurement as a guide to get close to where you should sit. After you've done your measurement, if you still think you could go a little closer then go for it. Use your own personal taste to judge the right distance.

Just The Right Height (direct view and tabletop projection TVs only)
This may be the hardest placement factor you can do to improve the perception of your TV's image. The right height of your TV is having the center of the TV eye-level with your seated position or just a little higher.

This can be difficult to accomplish as stands that are just the right height tend to be hard to come by, not to mention finding one that matches your decor. If you have the luxury to buy a stand after or when you buy your set, the best recommendation is to figure out how high the TV stand has to be to get your TV dead center.

To figure this out, measure how high your eyes are from the floor when seated. Then measure from the bottom of the TV enclosure to the center of the screen. The difference between those 2 numbers is the height at which the shelf holding the TV should be from the floor.

(eye height) - (TV's center height) = stand height

Getting your TVs screen near center greatly improves the TV's perception of size and quality. Having a TV setup dead center makes the TV seem bigger in size... which is always a good thing.

Audio Considerations
After getting your seating in the optimal viewing range if you find yourself sitting in the middle of your room you may want to find a different place to put your TV, or move away from the set a little further.

The reason for this is that sound produces odd nodes it the center of any room, providing less than optimal sound qualities. Your seating position for sound should be setup where you'll sit in either one of the thirds or fifths of the room. These areas, or dividers, are where your system will sound it's best. If you can't setup your room differently you may want to consider sitting further away from your TV. (Check out the Furniture Placement article in the Your Room area for more info.)

Try not to sit any closer than the optimal viewing range as the individual lines can distract from the film, robbing you of the experience (not to mention cause nausea and headache). It's always best to move away from the optimal viewing range if your room's acoustics force you to do so.