Answer: Television in the past was based on a maximum scanning resolution of 480 lines from top to bottom (520 x 480). This is the National Television System Committee standard. The easiest example is where an (old style TV) CRT display device displays an image by scanning a grid of phosphor “pixels” from the top to the bottom ... every second line at a time. Think of a screen door that’s made of 480 wires going each way. Now fill in with a brush the first line (left to right), then the third, then the fifth and so on until every second line is filled at the bottom. Start again from the top, filling in each even numbered line until all the lines are filled. That’s one full frame. The old CRTs did that 30 times a second or 30fps. This is called Interlace Scan.

As screens got bigger the flicker that became evident proved to be unsatisfactory. Then came Progressive Scan. This technique has the CRT scanning every line sequentially, or line one, then line two, then line three and so on until every line is filled. This is done 60 times per second, or 60fps. This resolution and scan rate is called SDTV. No longer using the same CRTs with the scanning cathode ray, Progressive Scan still stands for non-interlace and the way LCD and Plasma works, they switch the entire screen (all lines) on 60 times per second.

Answer: 1080p is the resolution used by Blu-Ray High Definition DVDs. The advantage of a 1080p TV is that the set will be able to display any signals now used by broadcasters and offered in movies. The 16 x 9 aspect ratio and the 1920 x 1080 screen resolution is considered to be the equivalent of large-format movie film used to film big-screen movies. Many years ago, this standard was set by the movie industry and it has become our TV standard. When you watch a regular DVD, you see a 16 x 9 display with an NTSC standard 480P picture. When you watch a Blu-Ray High Definition movie you could see anywhere from 480p or 640p or 720p or 1080p picture — whatever resolution the disc is recorded in. Your viewing screen may as well be able to take advantage of the best possible 1080p. Basically, the more pixels the better.

First of all, anything of higher resolution than SDTV (480p) is considered HDTV. In fact many early HDTVs were only 540p to 640p. (The “p” stands for - you guessed it - Progressive Scan). If you use our previous analogy, 720p screens are a screen made of 1250 wires strung from top to bottom and 720 from side to side. Rated resolution is 1250 x 720.