HDTV – Getting the Whole PictureSubmitted by SharpMan Editorial Team on Friday 15th October 2010
- All about aspect ratio.
- Types of TVs.
- Ways to use it.
Start Getting the Whole Picture
If you’re not watching a digital television, you don’t know what you’re missing.
Today’s new digital sets give you more picture, plus a sharper, brighter and more clear image -- in a set you can lift without getting a hernia. Sold? We thought so. But slow down there, Sparky, before you run out to buy… or worse yet, try to get the full skinny from a salesperson at your local department store, there are some basic things you’ll want to know. Read on for the SharpToys 411…
It’s All About "Aspect Ratio"
First, the facts:
- The "aspect" in "aspect ratio" refers to the shape of your TV screen.
- Standard television screens are designed to present images with a 4:3 aspect ratio.
- Movie studios shoot feature films in 16:9 aspect ratio (called widescreen).
- Networks have begun broadcasting popular TV shows in this same 16:9 widescreen format.
The difference in these ratios presents some problems that simply getting a bigger screen won’t solve. Here’s why.
For the last 60 years, television has been recorded and broadcast as an image with a 4:3 aspect ratio. If you have a 40 inch television, then your screen is 32 inches wide and 24 inches tall — a 4:3 ratio which results in a diagonal measurement of 40 inches. This was fine when all we watched were programs recorded in exactly this ratio.
Even movies were originally shot in 4:3 aspect ratio until around the mid-50s. Then, two widescreen formats appeared on the horizon and still dominate the filmmaking industry today: Academy Flat (1.85:1) and Anamorphic Scope (2.35:1).
When movies are broadcast on television (or viewed via DVD), they are shown either in widescreen or pan-and-scan format. On a TV with standard 4:3 aspect ratio, a widescreen format program will appear vertically centered, between black bars at the top and bottom of the screen. The picture uses only about 80% of your screen. Further, with pan-and-scan, the image is cropped to squeeze into the shape (or "aspect") of the screen, while still attempting to keep the most important portion of the picture in frame. This means you will likely not see activity that occurs at the far right or left of your screen.
The number one benefit of high definition television is that it fixes all this. HDTV screens are shaped to accommodate images in a 16:9 aspect ratio so you can always get the entire shot just the way the director intended and, you’ll always use the maximum possible amount of screen space to display it. Face it, size matters when we’re talking TV screens.
About Screen Resolution
Want to know how television works? Me neither, but we have to talk a little about the basics in order to understand the differences in resolution between traditional analog television and today’s digital sets. For starters, digital video signals come in two flavors: interlaced and progressive scan.
Traditional analog television paints an image (called a frame) on the screen in two interlaced parts. Each frame contains about 480 visible lines. On the first pass, the odd numbered lines are painted from top to bottom. Then the electron gun resets the beam to the top of the screen and paints the even numbered lines. It takes time to reset the beam to the top so there are 45 blank lines inserted in the signal to give the gun time to reset. For that reason, analog television resolution is referred to as either 480i or 525i ( 480+45=525, i for interlaced). This all happens very fast, of course. Each pass takes 1/60th of a second and, since it takes two passes to paint an entire frame, the frame rate is 30 frames per second. Although there is no noticeable flicker in the display, when 480 lines of an interlaced picture is blown up to fill a big screen television, the effect of this interlacing renders a less than sharp picture. Heck, you could miss a handoff in the backfield if you’re not watching closely.
Progressive scan, on the other hand, paints the entire frame in one pass, thirty times per second. Because every line is painted on each pass, the image is presented in much higher quality when enlarged. Resolutions are also considerably higher — typically rated as either 1080i or 720p. 1080i indicates an interlaced signal carrying 1,080 lines of vertical resolution and 720p refers to a signal carrying 720 vertical lines using progressive scan mode.
Are you still with me? Good, because now come the choices…
Display Types and Projection Styles
There are several types of digital television. Here’s the skinny on what all those letters mean.
SDTV: Standard Definition Television is basic digital television signal broadcast at a resolution less than 480p.
EDTV: Enhanced Definition Television is not high definition but does indicate at least a 480p resolution in either 4:3 or 16:9 aspect ratio and thus will provide a higher quality picture than the standard 480i. It also supports 5.1 digital surround sound.
HDTV: High Definition Television is high definition, obviously, and most sets accept video sources at either 1080i or 720p. There are, however, several types of HDTV technology on the market:
- CRT, or cathode ray tube displays are the cheapest, but they are also the bulkiest and heaviest of the breed. They can weigh a couple of hundred pounds or more. They are available in direct view and rear projection models. The direct view models aren’t generally available in sizes larger than 40 inches. Rear projection models are difficult to view from an angle other than straight on.
- LCD sets have a rear projection Liquid Crystal Diode display. They are a good value and are designed to last longer than plasma displays. They don’t suffer from image burn-in (the effect when a static image has been on your screen too long and leaves an imprint that’s visible even when the set is powered off). They have good image stability, but they don’t track motion as smoothly and they sometimes suffer burnout of individual pixels which cannot be repaired and are not covered by warranty.
- DLP Digital Light Processing is a rear projection technology that uses a very bright lamp and thousands of tiny mirrors. The sets are very light-weight, have excellent color and brightness and are generally immune to burn-in. The lamp will need replacing in 5000-8000 hours of use (a $200 expense).
- Plasma is still the top of the line in HDTV, offering flat screens so thin and light they can be mounted on a wall. But note that the price is still pretty high on these babies. Plus, they use more power than other types and are susceptible to image burn-in.
What You Can Watch
Before you make your purchase, you’ll want to check with your cable or satellite provider to make sure they offer a set-top box with HDTV capabilities. Most do, but some don’t… so check. There are a few caveats you should be aware of, as well. For starters, if you’re a Tivo subscriber, understand that Tivo does not currently offer a standalone DVR with HDTV capabilities. (DirecTV and Dishnet offer satellite receivers that combine HDTV and DVR capabilities -- if you’re a cable subscriber, however, there’s really no point to getting an HDTV-capable cable box because you won’t be able to connect the high definition output to the input on your Tivo recorder. You can still use your Tivo with your new HDTV set, you just won’t see the recorded shows in high definition.
The best, most reliable source of high quality digital video is a DVD player, preferably one that supports progressive scan. There are models available with 480p for less than $100. Once you have a TV with 16:9 aspect, you’ll also want to pay a bit more attention to the format of any videos (DVDs) you purchase. If you have a choice, make sure you get the widescreen version and although you won’t get a choice of widescreen aspects for a given movie, be aware that while 1.85:1 will completely fill your screen, 2.35:1 will fill it horizontally but you will still have small horizontal bars across the top and bottom of the screen.
What About Your Regular 4:3 Television Shows?
A lot of television is still broadcast in 4:3 aspect and you probably have more than a few videos and DVDs in your library that aren’t widescreen format. If you’re wondering what that looks like on a 16:9 aspect HDTV, keep reading:
In general, most manufacturers give you a choice between several ways of handling 4:3 aspect programming. Most commonly, these choices are:
- A format that actually puts the image up in the correct aspect ratio between black vertical bars
- An image uniformly stretched horizontally to fill the screen (this is the most popular option)
- A panoramic version that fills the screen and tries to keep the aspect correct in the center of the screen by stretching it only on the edges (this tends to have a fisheye look)
A little experimentation will tell you which mode is most pleasing to you.
Time Is Running Out
If you’re thinking this is way too much information and I’ll-just-stay-with-my-ten-year-old-Trinitron… think again.
The FCC has mandated that all television stations be completely converted to digital by December 31, 2006. After that date, anyone who’s still getting their television from the open air waves (i.e.: roof top antenna) will need a digital-to-analog converter to use their existing non-digital televisions.
That’s right… within the next year and a half, we’re all going to have access to pure digital TV feeds and the absolutely stunning pictures they are capable of producing. While you will be able to continue using your old analog set if it’s attached to a digital cable or satellite box (because they have built in converters) or, even by purchasing an external converter box to put between your antenna and your set, the FCC has actually provided you with the perfect excuse to get one of the quintessential guy gadgets: HDTV.
Gentlemen, start your engines.
For more information on the coming FCC requirements please check out FCC Consumer Facts.This article last updated on Friday 15th October 2010