What's the difference between 1080 and 768 resolutions for LCD TVs?

Is there a big difference between 1080 and 768 resolutions for LCD TVs? I am trying to decide between two Sony TVs -- the KDL-40X2000 and the KDL-40V2000.

I was told that the key is to find out if the resolution is interlaced (i) or progressive scanning (p). I can't see this on Sony's Web site tech specs on either of the models I am looking at. Can you help?

Peter Davies

Since the advent of high-definition, screen resolutions have been causing a great deal of confusion -- especially now that the new 1080p format has been introduced.

A screen's resolution is measured by the number of vertical picture lines x the number of horizontal picture lines -- for example, 1,366x768. Images are created by rapidly scanning these lines across the screen, starting at the top and finishing at the bottom.

There are two ways of scanning these lines:

- Interlaced (i) scanning splits the lines into two fields. Odd numbered lines are scanned first, rapidly followed by even numbered lines to produce a complete image.

- Progressive (p) scanning allows all lines to be displayed sequentially instead of using two alternate fields, which produces a smoother picture with less flicker -- especially with movement.

Both of the Sony models you are interested in will be able to play interlaced and progressive scanned images, but differences in resolution will determine which formats they will accept.

Resolutions vary greatly between screens, but to display high-definition images you'll need a screen with a minimum resolution of 1,280x720. A more common resolution with LCDs, however, is 1,366x768 -- as used by Sony's KDL-40V2000 model.

This allows the screen to display both commonly used 720p (progressive) and 1080i (interlaced) high-definition formats. It's difficult to distinguish between these formats, but 720p is said to produce smoother pictures while 1080i is more detailed. Although 1080i signals can be displayed using a 1,366x768 resolution, they will be slightly downscaled to fit, leading to a slight loss of detail.

To display 1080i signals in their entirety, or to use the latest 1080p format, you'll need a screen with a 1,920x1,080 resolution -- as used by Sony's KDL-40X2000 model.

Deciding which resolution to go for really depends on your usage. It's important to remember that whatever resolution you use, image quality depends on the source signal.

If you are more interested in watching HDTV broadcasts, the KDL-40V2000's 1,366x768 resolution will suffice. All current high-definition broadcasts use either 720p or 1080i signals and although 1080i signals require some downscaling, the effect on image quality is negligible.

If you want to watch 1080p or so-called 'Full HD' images used by next-generation Blu-ray or HD DVD players and games consoles, you'll need a screen like the KDL-40X2000 with a 1,920x1,080 resolution. These screens are more expensive, but they generally provide better image quality and will future-proof your screen for when 1080p broadcast signals arrive. But be careful -- not all 1,920x1,080 screens will accept 1080p signals, although Sony's KDL-40X2000 will.

Hope this helps.