What does HD (High Definition) Mean?
By Benjamin Curto ~ June 29th, 2009. Filed under: Theater, Video.
Trying to figure out what to buy or what you have and you just keep getting more confused? It’s reasonably easy to do considering most everyone who could help you probably has an angle of selling you something!
Let’s start with the basics, pixels. Televisions are a lot like mosaics where lots of small dots make a picture when you step back from it. Each tile (or dot) in a television is called a pixel, and those numbers people throw around are actually the number of pixels. The more of them there are, the better a picture will look, just like a mosaic!
Standard television is typically 480i (480 horizontal lines… we’ll deal with the ‘i’ later), anything (read it) ANYTHING above this can be classified as high definition! This means not all high definition is the same, there are many different levels including: 720i, 720p, 1080i, and 1080p. The number always tells you how many horizontal lines the screen has, more is better. That was simple! There is more if you’re interested though…. For example are you curious how many vertical lines there are?
That’s more of a format question… the old style ‘square’ screens are a 4:3 ration, meaning it has 4 vertical lines for every 3 horiztonal lines where as newer screens are almost all ‘widescreen’ which is synonymous with a ratio of 16:9 meaning it has 16 vertical lines for every 9 horizontal lines. In today’s market you can ignore the screen format for the most part as virtually all LCD, plasma, and projectors on the market use a 16:9 widescreen format.
Let’s go back to that ‘i’ (and that ‘p’), it stands for ‘interlaced’ (and ‘progressive’ respectively). Interlaced menas it draws every other line on on it’s first pass (1, 3, 5, 7, 9, …etc) then every other line on it’s second pass (2, 4, 6, 8, 10…etc). Progressive means it draws every line on every pass. How much better is progressive? Make a picture book with 100 post it notes of a ballerina dancing…. then remove every other page and flip through it! Most people prefer 720p over 1080i, even though there are less lines/dots the picture is move vibrant because it’s drawn every pass.
What else contributes to the quality of the screen/picture? Well the technology used is a large factor (LCD, DLP, Plasma, CRT…etc), the brightness and contrast ration, and for some technologies the refresh rate. Those will all be discussed in future entries though!
I need 1080p now! Of course everyone does! Be careful though, remember what your screen can diplay is limited by what is plugged into it. A VCR that plays a 480i picture will still just be a 480i picture nomatter what screen it’s on. Likewise standard cable/satelite programming won’t improve much with an HD screen unless you upgrade to HD programming. Once you have an HD video source to plug into your television you need to make sure you have the right cable between the two otherwise it’s all a waste!