SDTV Vs EDTV Vs HDTV Differences

This article covers the NTSC (National Television System Committee) only. Which is the television standard in North America.

One walk around the big box department stores and you will find a number of TV's on display for sale. Known as the "Wall of Eyes" (WOE), it's a display meant to catch your eyes so that you can make a purchase as quickly as possible. Usually, they will have on the description near the TV that will show SDTV or EDTV or HDTV's. This is an explanation of the three types of displays.

Here are the types of display.

SDTV - Standard Definition TV - Resolution is 480i

EDTV - Enhanced Definition TV - Resolution is 480i and 480p. Supports wide-screen.

HDTV - High Definition TV - Resolution is 480i, 480p and can vary amongst the different High Definition sources. Supports wide-screen.

The resolution for HDTV varies depending on the manufacturer and the model number so you have to pay close attention to what is advertised and to what is written on the box or manual of the TV. You should always see if you can find the manual of the TV on the Internet or in person at the store and not rely on what the sales person says or what the store display says.

Here are the different resolutions of TV's: 480i , 480p, 720p, 1080i and 1080p.

What on earth do the numbers and letters mean? It's fairly simple, but a little explanation is needed.

Let's Cover the number portion first. The numbers are the lines of resolution that the television can display.

In 1941 a standard was developed for broadcasting video signals to televisions, this standard was called NTSC. The NTSC standard called for 525 lines of resolution, only of which 486 lines are actually visible. This up until the advent of HDTV was just known as a TV signal or standard TV. In the late 1980's a standard was developed for HDTV that called for 720 lines of resolution to show a much sharper image. Right around the same time another standard was being developed that had 1080 lines of resolution. Both types of resolution 720 and 1080 are considered high definition and both are gaining popularity in the United States with 30 percent of American households having one at this writing.

Quick Reference: 480 = 486 lines of resolution, developed in the 1940's, 720 = 720 lines of resolution, developed in the 1980's, 1080 = 1080 lines of resolution, developed in the 1980's. The letters behind the numbers are how the image is displayed, either interlaced (i) or progressive (p).

In the 1930's RCA engineer Randall C. Ballard invented interlace broadcasting. This allowed a TV signal to be broadcast without taking any more bandwidth. It does this by alternating every other line in a TV signal so that only half of the screen is shown at any one moment in time, the rest of the picture is sent immediately afterwards. The principal works like this: The signal is broken in two parts, odd lines and even lines, these are known as fields. Each of the fields are broadcast separately. The picture then only consumes half of the bandwidth. Each field is sent so rapidly, that the human eye will perceive the image as one picture, not 2 fields. The phosphors in the TV will remain lit long enough for the alternate field to be filled in. This can be easily seen when you have a VCR on pause, the image will jitter, this is the interlace working.

In the 1980's the popularity of progressive scan started to take hold. Though developed early on in TV's, progressive scan required too much bandwidth to be broadcast at the time. Progressive scan sends all lines of resolution to the TV at once, allowing for a sharper image. Progressive scan also purports wide-screen.

Progressive scan certainly has an edge on Interlaced scan when it comes to showing a sharper image, however you must remember that at this time, broadcasters still transmit using Interlaced scan. Using a EDTV or HDTV to receive an Analog broadcast will not be any different than using a SDTV to pick up the same analog broadcast. The difference then lies in which type of signal you want to receive.

Analog Broadcast (broadcast and standard cable) = 480i = Compatable with SDTV, EDTV, HDTV

VHS = 480i = SDTV, EDTV, HDTV

DVD using composite = 480i = SDTV, EDTV, HDTV

Blu-Ray and HD-DVD composite = 480i = SDTV, EDTV, HDTV

DVD using S-Video = 480p = EDTV, HDTV

DVD using component or HDMI = 480p = EDTV, HDTV

Blu-Ray and HD-DVD component or HDMI = 720p, 1080i, 1080p = HDTV

HD Cable or satellite = 720p, 1080i, 1080p = HDTV

I hope that this article sheds a bit of light on the different standards of TV and their acronyms. I suggest getting the TV that meets your needs and not the needs of the sales person trying to sell you the TV. If you only plan on watching standard analog TV broadcast through cable or through the air waves for the life of the TV, the get a SDTV, just be sure that you can either add a converter so that you can watch digital TV in the future. If you want to watch standard DVD movies in their highest resolution, then a EDTV will meet your needs, but again make sure that you can add a converter to watch digital TV in the future. If you want to watch the best that TV technology has to offer now, then get a HDTV, but don't be too surprised by the price tag.

(C) 2007 Andrew Dansby

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