HDTV stands for High-Definition Television, a class of TV that is identified by its resolution. To be considered high definition, a television must be at least 720p. Most modern TVs are high definition, ranging from 40 inches or below up to about 60 inches for a high-end consumer model, even more with projection technologies. Concept TVs have been demonstrated going up to 150”, but none that big have ever been released and sold on a mass scale to consumers. Let’s look a bit closer at resolution and how it is measured in order to better understand HDTV.
Television images are made up of thousands of little dots called pixels. (Technically, a pixel is the intersection of two lines, but it is much easier to think of them as lines of dots that make up a grid.) These are measured by the number of horizontal lines of resolution. A 720p television has 720 horizontal lines of resolution, and 1280 vertical lines. Older TVs had a 4:3 screen ratio, but HDTV has a 16:9 screen ratio, meaning that if it has 720 horizontal lines of resolution, then multiply that number by 16 and divide by 9, and you get 1280, the number of vertical lines of resolution. 720p is the smaller of the common HDTV sizes, the bigger and more common size is 1080p (that’s a 1080 by 1920 screen resolution).
You will also notice a letter after the resolution number. That letter is either “P” or “I,” and it tells whether or not the screen is interlaced. If the screen is interlaced (ends with an “I”), then it only refreshes half of the screen each frame. Though it is an almost unnoticeable difference, you are effectively only getting half of the vertical resolution, so you want to get a TV that has a “P” after it.
There are two main types of HDTVs, plasma and LCD. Plasma TVs show smoother frame transitions and look glossier but they are very reflective, and are not good for rooms with lots of windows / sunlight, so most people opt for an LCD TV, which is still a very good TV.
Remember when you are looking for your next TV that you want at least 720p to get HD, and that ideally you want to get 1080p to get the highest resolution possible.
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