This week, we continue our guide to the purchase of high-definition televisions (HDTVs) and the definition of some of the technical terms for these equipment.

We kick things off with aspect ratio: This spec is much simpler than the others. The two most commonly seen aspect ratios for home entertainment are 4:3 (also known as 4x3, 1.33:1, or standard) and 16:9 (16x9, 1.78:1, or widescreen).

Traditional TVs that were square-looking had an aspect ratio of 4:3. Most HD signals (if not all) today have a native aspect ratio of 16:9. If you have a widescreen TV and you are viewing standard programming, the picture will appear in letterbox format. This means the picture will appear with black sections on either the side or at the top and bottom of the screen; this is called pillar-box. To get rid of the pillar-box black bars, there are a few options: you can stretch the image or zoom in on the picture and fill the screen. Both options will either cut off some of the image, distort the image or both. Ensure the TV you are planning to purchase has at least a 16:9 aspect ratio.

Resolution

720p, 1080i, 1080p what does all this mean? This is the actual resolution of your TV. 720i means the picture is 1280x720 pixels, sent in interlace (more on interlace further on in the article). While 720p means the picture is 1280x720 pixels, sent in progressive scan (more on progressive scan further on in the article). 1080i is 1920x1080 pixels, sent in interlace and 1080p is 1920x1080 pixels, sent in progressive scan.

The highest resolution for HDTV today is 1080p; however the difference between a 1080p and a 720p resolution is not evident on smaller TVs like 46 inches and under. You will begin to see the difference when you get to 50 inches and higher; Reasons being the bigger the picture is stretched, the more details are revealed and that's where having more pixels becomes more important. 1080p which is 1920x1080 pixels has much more pixels than a 720p which is 1280x720 pixels. So if you are on a budget and you find yourself a nice HDTV that has all the specs that this article spoke about, but cannot display images in 1080p but can do so in 720p as long as that TV is below 47 inches, trust me it's a good buy. If you are not on a budget and money is not an issue, then by all means get a 1080p HDTV no matter the size.

Interlace:

Have you ever seen 1080i, 1080p, 720i or 720p printed on HDTVs and thought what does the letter after the number mean? The i represents 'Interlace' while the p represents 'Progressive'. This is how the image is scanned on the TV either interlaced or progressive scan. Let us look at this in a very simple way; the standard NTSC system uses 525 scanning lines to create a picture (frame).

Interlaced scan means the lines that make up the picture on your TV screen are drawn in an alternating fashion. In other words every 60th of a second, every other line making up the complete frame is scanned. Then, a 60th of a second later, the lines in-between are scanned. So the process would be something like this for interlace scan: 1, 3, 5, 7, 9:525 then a 60th of a second later the other portion of the image is scanned; 2, 4, 6, 8:524.

Remember NTFS uses 525 lines to create a picture so only half of that which is 262.5 lines are scanned each 60th of a second, for interlace scan.

Progressive scan explained: Progressive scan differs from interlaced scan in that the image is displayed on a screen by scanning each line (or row of pixels) in a sequential order (1, 2, 3, 4, 5:525) rather than an alternate order, as is done with interlaced scan.

Progressive scan draws the total picture in 60th of a second; unlike interlace which draws half of the image in a 60th of a second, then the other half in the next 60th of a second. By progressively scanning the entire image every 60th of a second rather than interlacing the image, a smoother, more detailed image can be produced on the screen that is perfectly suited for viewing fine details, such as text, and is also less susceptible to interlace flicker.