A common question when buying a new TV is "What size screen should I get given that I sit at distance X from the TV?" or alternatively, "What is the best distance to view a TV from if it has a screen size of Y?" or even "Is it worth me getting 1080p or should I stick to 720p?"

The screen size (usually measured in inches) is the diagonal size of the display area measured from top left to bottom right. When shops used to sell the old tube TV sets the manufacturers could get away with quoting the size of the glass which extended beyond the visible screen. With LCD and Plasma TVs they are no longer allowed to do that, so you can be sure that the quoted size is the actual size of the picture you will be viewing. This means that a 32 inch flat screen TV has a slightly bigger picture than the 32 inch telly you were used to. Furthermore, the new technology allows much larger screens to be fabricated and the sweet spot that the panel makers are targeting for highest production volumes is now around 46 inches. Of course you need to take into account the space you have for it in the living room and your budget.

The size of your screen also needs to be consistent with the screen's pixel resolution and the typical distance you view it from, so let's look at the different resolution standards next. The resolution is usually quoted in terms of the size of the matrix of pixels which make up the screen. For example a resolution of 1366x768 means that the picture is made up of an array of dots in 768 lines down the screen, each having 1366 points across. That makes about one million pixels in total. As you probably know by now, there are two main resolution standards in use for high definition TV. The base HD standard of 720p is 1280x720 but there is also a higher standard known as "Full HD" or 1080p which has a resolution of 1920x1080 pixels. You should compare these with the standard definition (SD) widescreen pictures using the old PAL system which were equivalent to a resolution of 1024x576. In fact, as can be seen in the diagram below, the 720p high definition standard is not massively bigger than the PAL standard. It was really defined with the US standard NTSC in mind which had a much poorer resolution. For European viewers there is much more incentive to opt for a screen which supports the higher Full HD standard. Many HD TV channels broadcast with a data bandwidth that would not justify Full HD resolution, but HD-DVD and Blu-ray disks provide a much higher quality picture that needs a Full HD screen for the best appreciation.

So a Full HD purchase is certainly justified for the ultimate home movie experience, but it is going to be more costly than 720p and would be a waste of money if your screen is not big enough relative to your normal viewing distance. The viewing table below should be used to help you choose the right screen size for your circumstances. For example, if you are aiming for a 40 inch HDTV and your typical viewing distance is 8 feet, then it falls into the 34"-42" range that indicates you should get a 720p resolution screen. There would be no point in buying a Full HD screen at that size and distance unless your eyesight is significantly better than average.

If you have a TV with a specific screen size and resolution  in mind you may find this table of optimal view distances more appropriate.

Add a comment

Posted by ZettaVolt on 07 September 2008 16:53:00 BST #