what is the difference between full hd and hd ready

If you have figured out all the other terminology involved with modern television technology, I am quite impressed. Between HDMI, Component, S-Video, 1080p, 1080i, 720p, 480p, Blu-Ray, HDDVD, 5.1, 7.1, 2.1, PAL, NTSC and oh, so many more elements of HDTV technology, if you have really got it all figured out except "HD capable" and "HD ready", then you're ready to be lead salesperson at Circuit City, I think!

Let me start with your answer, then I'll offer up a bit more information about high-definition television technology and related. In a nutshell: HD-ready sets have the HDTV program receiver/decoder built-in, while HD-capable sets require the addition of an external receiver/decoder needed to receive digital broadcasts. As I'll be writing about later this week (stay tuned for the link here) all television broadcasts will be 100% digital starting in 7 February, 2009, so if you have a TV that requires an analog signal, you will need a converter. Some companies don't want to admit that their TV systems aren't ready for a pure-digital television signal coming into the device, though, so they say that they're "HD-capable". Honestly, it seems to me that with the addition of a simple digital-to-analog converter (see DTV2009.gov) you could say that every analog TV is "HD capable".

My advice: it'd be insane to spend the money for a high-def television that was only "HD capable" at this point in time. For the same price, you should unquestionably be able to find an alternative unit that is HD ready, and skip the silly converter box entirely when the big switchover comes to pass in 2009.

While you're reading, though, a quick primer: North American television has a fast refresh rate of 60 frames/second (versus the European PAL format which works at 50 fps), but the way it does that is through a sneaky technology called "interlacing". Interlacing means that half the image is sent on each refresh, alternating between the even numbered and odd numbered horizontal lines of information. So you get lines 1, 3, 5, 7, etc., the a 60th of a second later, you get lines 2, 4, 6, 8, etc. Works faster than your eye can recognize the sleight-of-hand and the result is smooth transitions and smooth motion, even during action scenes.

Problem is, it really would be better to have all the image information each sixtieth of a second and you'd have an image that would be ostensibly twice as visually stable and attractive. That's what's called "progressive" video and each frame has lines 1, 2, 3, 4, 5, 6, etc. In the early years of television technology there simply wasn't the bandwidth to send that much information, but now there is, and more.

The result is that the default TV video signal is 480i, which means that your entire image is only comprised of 480 horizontal lines, even on a really big screen. Worse, it's still interlaced, so each frame is really only 240 horizontal lines of information. Not much when you have a screen the sprawls across 40-50" or even larger. (caveat: many TV systems can "interpolate" and artificially produce transitional information between lines, effectively producing a higher resolution image. This can also work with DVD players and is generally known in the industry as upscaling, taking a low resolution image and artificially boosting it to a higher resolution format)

This is where things get a bit confusing, because while 480i is the standard for TV signals, there are now signals in 480p (progressive, not interlace, but still only 480 horizontal lines), 720i (a boost up to 720 horizontal lines, but still interlaced), 720p (same resolution, but progressive), 1080i (high def resolution of 1080 horizontal lines, but still interlaced) and the holy grail of modern HDTV, 1080p.

All being equal, you want to have an HDTV that works with 1080p signals as that's true high def. Any model I've seen that does that can also handle all the other lower-resolution signals that are produced by various devices too, all the way down to 480i, the "old" format.

*phew*

I hope that helps you understand some of the core technologies with your new HDTV unit. . Sony Brevia 1080p 40" LCD TV, Highly recommended!)