1- WHY ARE ALL HDTV'S WIDE SCREEN?

Movies weren't allways wide

Thomas Edison created the motion picture system long before television entered the scene. When it did, it adopted the same ratio of picture height to picture width that the movie industry used. However, because they were afraid that people would no longer go to movies if they were available on TV, Hollywood started to make their screens wider so that they wouldn't easily fit on TV. As a result, we have two aspect ratios: one for watching TV and one for movies.

Making movies fit

Old TVs have a squarer 4:3 aspect ratio. That means that for every four inches across your screen measures, it is three inches tall. For instance, a set that measures 12 inches across is 9 inches tall. Movies have a wider ratio of width to height, closer to 16:9 (that same 9 inch tall TV is now 16 inches wide).

Pan-and-scan chops the sides

To make movies fit on an analog television, one of two things need to done. First, the movie can be formatted to fit. However, if the film is squeezed left-to-right, then everyone appears much skinner than they should. So, instead, the sides of the movie are cut off and you don't see it in all of the majesty that the director intended. The frame you see is moved or "panned" left or right depending on where the action is on the larger movie frame. This is called "pan-and-scan".

Black bars reduce picture quality

The other method shows you the whole movie, but has its own problems. In this case, the whole film is scaled down, left-to-right and top-to-bottom, until the frame fits within the TV. Now everyone looks right and you see the whole movie & and you have black bars above and below the frame. It also means that, of the 480 lines of resolution, the film is only using those in the middle of the screen and is not as detailed as it should be.

Fix the set, not the movie

The solution is to stop trying to fix the film and fix the TV. Widescreen TV's not only show movies better, they also provide a closer match to how far our eyes see side-to-side. This is a huge benefit for sports. When watching a football game, you'll be able to see more of the field, or the whole ice rink and get a better feel for how the play unfolds.

Another word that you will hear often when people discuss DTV is "pixel". Pixel is a contraction of the words Picture Element. These are the dots that make up the image we see on any television or computer monitor and there can be as many as one million of them making up a DTV picture.

2- WHAT IS A PIXEL?

A pixel is worth five words

Any one pixel is made up of five pieces of information: vertical location, horizontal location, red brightness, blue brightness and green brightness. Together these pieces of information allow the television to place a dot of the right color in the right place on the screen. When combined with all of the other pixels that fill the screen, a single frame of video is produced. The signal then tells the television how to change or "refresh" each pixel up to 60 times in a second.

The end result is the image that you see on the screen and its constantly changing pixels.

As you start to learn about DTV, you quickly discover that there are a lot of confusing terms and numbers. In this section, we'll shed some light on those starting with the acronyms SDTV and HDTV.

3- WHAT IS THE DIFFERENCE BETWEEN SD AND HD?

SD-  Standard Definition

There are two basic DTV broadcast standards: Standard-Definition television (SDTV) or High-Definition television (HDTV). SDTV programs are broadcast use 480 horizontal lines to produce and image. Each line is made up of pixels: SDTV has 640 pixels per line; almost twice what we see on an analog TV broadcast.

HD – High Definition

There are two High Definition (HD) standards. HDTV programs use either 1080 lines with 1920 pixels per line or 720 lines each with 1280 pixels. These are always showing a widescreen picture. Because there are more pixels on the screen, the resulting picture is much more detailed than SDTV.

Describing the difference between interlaced (the "i") and progressive (the "p") is easier to show than to describe with words. So, as you read the description below, keep referring to the animation above.

4- WHAT DO "i" AND "p" MEAN

Interlace – odd lines then even lines

To trick the eye into seeing motion, the image on your screen needs to show 30 frames per second. But to reduce eye strain and completely smooth out motion, 60 frames per second is preferred. Because of technical limitations when the TV signal was developed, to achieve the necessary 60 frames per second, only half the signal was shown at a time: first all of the odd lines and then all of the even lines. Because the TV set switched these alternating sets of lines, called "fields", every 1/60th of a second, your eye"laced" them into one frame of video; a process called "interlacing". To denote this, an "i" is added to the end of the number of visible lines of image: 480 lines shown interlaced are called 480i. Interlaced video does have drawbacks: thin lines and text may appear to flicker and fast-moving objects can become less distinct.

Progressive – all of the lines, every time

Because technology has advanced since the original signal was created, we can now show video at 60 frames a second without interlacing them. This is called "progressive scan" and displays all the lines of video progressively, from 1 to 480. Images are more distinct and free of flicker, and motion is smoother. That’s what the "p" means in 480p: the image is shown in progressive scan. Most DVD players now support the option of 480p output for digital TVs that can handle this type of signal.

In HDTV, interlacing is still used in order to fit all of the picture information into the bandwidth or down the cable line. This is why you will still see the "i" at the end of 1080i.

5- WHAT DOES CONTRAST AND COLOR MEAN?

Because HDTVs are all displaying the same resolution,'lines of resolution ? are no longer a good way to judge the quality of a set; it’s either 480 if it is a Standard Definition set or either 720 or 1080 if it is a High Definition set. As a result, people have focused on a few other numbers in order to judge picture quality: Contrast Ratio and Color Processing. Keep in mind, having good numbers in either or both of these should not be the sole judge of a new television. Nothing beats seeing the picture first hand.

Contrast Ratio – darkest to brightest

Contrast Ratio is a comparison of the light output from the brightest image a set can produce to the darkest. It is not only how bright the set is, it is also how well that light is controlled. It is not very difficult to make a television bright; all you need to do is add more energy to the picture tube or other light source. However, when the brightness is increased, it not only makes the bright parts brighter, but can also make the parts of an image that are supposed to be dark a little grey. A high contrast ratio means that the manufacturer has done a good job controlling how the light is applied to the set. It also means that you will more easily be able to see the subtle differences in darker shades that might get lost if the set is unable to produce a deep black.

Applying color to contrast

The Color Processor’s job is to make sure that that contrast ratio is applied correctly to each of the primary colors that the set combines to produce all the different shades and hues that you see on screen. However, with a digital signal, the total number of shades that you see is controlled by the number of bits that the color processor understands, the higher the better. For instance, a set with an 8-bit processor can produce 256 different shades of red, 256 of blue and 256 of green for a total of 16.8 million colors. That sounds like a lot, but with only 256 shades of each primary, our eyes can see the borders of each shade making a face look like a topographic map. If the color processor could handle 10 bits of color, then it could produce 1024 shades of each primary and over 1 billion total different colors. This doesn't quite eliminate this noise, but it gets close.

One of the final terms that you will see on a digital television determines how it receives the digital signal. There are digital monitors, digital televisions and digital cable ready televisions.

As you read this section, keep in mind that ALL of these sets can still receive the older, analog signal no matter what kind of digital tuner they have or don't have in them.

6- WHAT IS A DTV MONITOR AND A DTV TELEVISION?

Monitors – no DTV tuner

If a set is called a Digital Monitor that means the set is able to display a particular resolution (Standard Definition of at least 480i, Enhanced Definition of at least 480p or High Definition of 720p or 1080i) but that it needs an external tuner box to receive the signal. This box could be a cable box, satellite receiver or a tuner with an antenna connected to it. These boxes are then connected to the TV.

Digital Televisions – built-in DTV tuner

One that is called a Digital Television has a DTV tuner built into it that will receive the DTV signal through an antenna. Connect the appropriate antenna to the connector on the back and you ?re receiving DTV. However, these sets will still need an external box for high definition signals over cable or from satellite.

Digital Cable Ready

A Digital Television that is Digital Cable Ready is one that with a special slot in the back. A special card is available from the cable company, called a CableCARD!", which will allow the television to decode all of the cable channels, including those in high definition. These sets still need an external box in order to receive a signal from satellite or to use some of the advanced cable features like Video-on-Demand and Pay-Per-View with out a phone call.

ED – Enhanced Definition

This designation defines the capability of a television that is better than SD, but not up to HD standards. Basically, it takes SDTV and makes it widescreen. This expands the horizontal pixel count to 852 thereby offering more detail than SDTV. There is another difference we'll discuss when we explore the ?i ? and the ?p ? in the next section. There can be ED monitors, ED TVs and ED TVs with Digital Cable Ready tuners.

As we talk about the different types of DTV displays, keep in mind that they can be categorized into two distinct groups: those that scan the pixels one at a time and those that assemble them in memory first and display them all at one.

7- WHAT IS THE DIFFERENCE BETWEEN SCANNED AND FIXED PIXELS?

Scanning what you’ve got

The scanning displays are those based on cathode ray tubes: Tube TVs and Rear Projection Tube TVs. These use an electron beam to illuminate one pixel at a time, moving across one the screen to make a line of pixels. It then moves down and repeats the process. Because the pixels are not fixed on the screen but are defined by the spot of the electron beam these types of displays can easily adjust from one type of DTV signal to another, say from 720 lines to 1080, without having to convert the signal.

Fixing the picture

All of the newer display categories (LCD, Plasma and Micro-Displays) are termed fixed pixel displays because they can only show one resolution. This is because the pixels are not defined by a moving beam, but by stationary light elements: a liquid crystal or a mirror or a plasma cell. As a result, every pixel must be assigned a value even if the DTV signal does not contain enough information to do that. This means that all signals that are not the native, ?golden ? resolution of the display must be scaled to fit. Often this means adding information to the picture; guessing at what the pixel between two other pixels might be based on the information for those two, real pixels. This is called ?interpolation. ? If the fixed pixel display’s native resolution is low enough, this may mean throwing out information to make the picture fit.

The positive side of all this scaling is that, no matter what the image, the TV will attempt to make the picture look its best. For instance, all interlaced shows are automatically converted to progressive. Of course, those shows that are broadcast in the display’s native resolution will always look the best.

8- TYPES OF TV'S

It all started with tubes

Cathode Ray Tube (CRT) or, more simply, Tube TVs are the oldest display technology. Engineers have been building and refining this type of TV since the early 1930s. As a result, it is the standard against which all other types of displays are measured. No other technology is able to produce the same combination of color accuracy, brightness, contrast and viewing angle. While other display types might exceed tube TVs in one or two of these areas, none are better in all of them. Also, most of our homes and furniture are designed to house this type of set.

Small and heavy

That said, there are some downsides to tube sets. They are heavy because of the glass used to make the tube and screen. This also means that they are usually deeper than some of the other formats; there is no easy way to hang one of these on a wall. Finally, because of the weight and the vacuum inside the tube, they are only available in screen sizes up to 40 inches with most 32 inches or smaller.

Tube TVs advance into the 21st Century

Newer tube TVs are available with slimmer depth. Technological advancements have been made by several manufacturers that shrink the back of the tube. These new, slim designs are unique and affordable making them a popular choice for many people.

When shopping for a tube TV, here are some of the things to look for:

How dark is the screen when it is turned off?

This tells you how close to a real black the set can produce; the darker the better.

Is it big enough?

The farther you sit from the set, the larger it needs to be in order to create that cinema-like experience.

How fine is the grain of the phosphors that make up the pixels in the tube?

The finer it is, the finer the detail of the picture at any resolution. While many manufacturers don't publish this information, if they assign a name to their phosphors, it is usually better.

Will the set fit in your furniture or TV niche?

Even though the furniture says that it can accommodate a 32 inch set, it may not be able to if the speakers are mounted on the side or if the set is too deep.

There are several types of Micro-display TVs but all of them share a few things in common. They are all "rear projection sets" meaning that light is projected onto the rear of the screen. This allows them to deliver a large image, some in excess of 60 inches, while still maintaining a slim, table-top cabinet. All of them use a lamp as a light source that must be replaced after a certain amount of time. The type of micro-display is determined by which imaging device is used. Here is a brief over view of the different types:

DLP – Digital Light Processing

This is a technology created by Texas Instruments. It creates an image by reflecting light off of hundreds of thousands of hinged mirrors mounted on a chip that is slightly larger than a postage stamp. Pivoted in one direction, an individual mirror sends light through the lens to the screen; pivoted the other direction, no light gets to the screen. When combined and repeated 60 times a second, a video image is produced. Different colors are created by inserting a multi-colored filter between the lamp and the reflecting chip.

LCD – Liquid Crystal Display

These micro-displays shine light through three small LCD panels. Light from the lamp is split by special dichroic mirrors into red, green and blue beams. Then each of the different colors is sent through one of the three panels which determine how much of that color makes it to the screen for each pixel. After the panels, a prism recombines the three light beams and sends them out the lens to the screen.

LCOS – Liquid Crystal on Silicon

This is very similar to LCD except that light reflects off one of three panels instead of shining through them. There are a few variation of this technology, most notably SXRD from Sony and D-ILA from JVC.

Here are some things to look for when comparing Micro-display TVs:

How close to the set do you need to be in order to make out individual pixels?

If you can't see them until you are very close to the set, then the image will appear smooth and film-like from the seat.

What is the contrast ratio of the set?

Contrast is more than how bright the set is, but also how well it can reproduce deep black.

What is the "native" resolution of the set and how does it deal with other resolutions?

These are fixed pixel sets, so they must convert all other non-native resolutions to that one. How well is each able to do it?

How long will a lamp last, on average?

The lamp that is in these sets will wear out. When that happens, it can be replaced and will make the picture from these sets look virtually new. However, do ask how much does that lamp costs to replace?

Table or wall: the choice is yours

Plasma TVs have revolutionized how the television fit into our homes. No longer is it necessary to sacrifice an entire room to get a big picture, instead hang it on the wall (though most people don't bother). And with a choice of sizes from 37 inches up to 80, big home theater can fit in any room. In fact, several companies make brackets for plasma sets that allow them to be tilted, swiveled and even swung out on arms for even more creative mounting options.

A refined technology

While early plasma sets were bright, they were not known for their ability to produce deep blacks and had problems with screen aging. Most of these problems have been fixed, even to the point where "burn-in", the uneven aging of the picture, is now no worse than that on a tube TV.

Here are some of the questions to consider when shopping for plasma TVs:

Where will the set be placed in the home?

This has more to do with light than whether it will be mounted on the wall. Because plasmas use a glass coating, they are susceptible to glare. It is a good idea to mount then on the same wall with windows or light and not across from them.

What is included with the set?

Most plasma TVs come with a table stand, but some don't. A few don't even come with speakers.

Is the HD TV tuner built in?

Because Plasma panels are thin, they often do not have space for this tuner and, even if they do, they often are not CableCARD ready.

What is the "native'"resolution of the set and how does it deal with other resolutions?

These are fixed pixel sets, so they must convert all other non-native resolutions to that one. How well is each able to do it?

What is the altitude where you live?

Because plasmas are gas trapped between glass, at high altitudes where the air is thin the gas expands pushing the glass apart. The set has to pump more energy at the cells causing them to buzz and, in extreme cases, to stop working. This is only an issue in areas that are 6500 feet above sea level or higher. 

LCD's

New to television

While LCD TVs are relatively new, the technology has been around for a while in the computer world as monitors. LCD displays share many of the attributes of plasma TVs: they ?re thin, they hang on a wall and they have only recently become available in the home television market. However, that’s where the similarities end. LCD TVs are available in a wider variety of sizes starting as small as seven inches and ranging up to 57 inches. Also, because most LCD TVs don't use glass on the face plate, they are less susceptible to glare and can be used in rooms with more light.

LCD (liquid crystal display) panels work through the use of polarizing crystals. These crystals are placed in front of a constant light source, usually a florescent bulb. When electricity is passed through the crystals, they block a certain amount of light from the bulb; more electricity makes the crystals block more light. By grouping sets of crystals in threes (one red, one green, one blue) a pixel is made and colors can be formed.

Bright and efficient

Because they use florescent bulbs, LCD TVs can produce a bright image. It also means that they are energy efficient. However, because the bulb is always on, they often struggle with the dark areas of a picture. Also, many LCD sets do not respond quickly to fast motion resulting in motion blur on the trailing edges of fast moving objects.

Here are some questions to ask when shopping for LCD TVs:

What is the set’s "response time"?

This is an indication of how well the panel will respond to motion. The smaller the number, the better.

What is the contrast ratio?

A higher number means that the set will do a better job showing detail in dark areas of the screen.

What is the "native" resolution of the set and how does it deal with other resolutions?These are fixed pixel sets, so they must convert all other non-native resolutions to that one. How well is each able to do it?

What is included with the set?

Most will come with a table stand and a few with the wall bracket as well.

Is the HD TV tuner built in?

Because LCD panels are thin, they often do not have space for this tuner and, even if they do, they often are not CableCARD!" ready.

How far "off-axis" can I view the set?

Some LCD sets will change color or dim as you move off to the side.

PROJECTION TV

These are the large boxes that used to be the only choice for a home theater-sized screen. Today, these sets have been eclipsed in popularity by many of the new displays, but can still represent a good value & if you have the space.

The power of three

Rear Projection TVs use three CRTs, the 'tube" in tube TVs, that each project one of the primary colors through lenses, off of a mirror and on to the back of a screen, much like Micro-display sets. However, because they basically use three small tube televisions to create the image, it is difficult to build them into small cases.

Keep them in line

RPTVs share many of the same benefits as tube TVs: they are bright, have accurate color and can produce a nice, deep black. However, the three tubes can drift out of alignment creating colored edges. This can be fixed with by "converging" the set periodically. Also, they will dim as you move off of the centerline of the set, both vertically and horizontally.

Here are some questions to ask when shopping for a Rear Projection TV:

How much space does it need?

These are floor-standing sets in big cabinets. Make sure there is room for them.

How many people will be watching this?

The manufacturers of these sets spend a lot of time focusing the light from the three CRTs out the center of the screen. As a result, someone sitting directly in front of this type of display is treated to one of the most natural pictures available. However, people sitting to the sides or below the center may not see as bright an image.

How easy is it to "converge" the set?

The three tubes will get out of alignment. What menu options can correct this problem?

A movie theater in your home

Front Projection systems are the ultimate in home theater because they fit the room very much like a film projector: shining light across the room onto a screen. As a result, the screen size can be adjusted to fit a room or wall exactly. In fact, for the biggest possible image, front projectors are it: some of them are capable of creating a 300 inch image!

Different flavors

These systems use all of the same technologies as micro-display TVs as well as three-CRT systems similar to those found in RPTVs. All of the same benefits of each of those technologies also apply here. However, unlike all of those technologies, you now have to choose a screen as well. Because they come in a variety of sizes, mounting options and reflectivity characteristics, they can affect the viewing experience almost as much as the projector itself. The screen’s importance is why these are often called "two-piece" projectors.

Keep them in the dark

There are a few other things to be aware of in these systems. To get an accurate picture, the room should be dark; these systems can only produce a black that is as dark as the room. Also, the larger the screen, the dimmer the picture will be. A projector only has so much light to spread across the screen so the bigger the screen, the thinner that light is spread.

Here are some questions to ask when shopping for a front projection system:

What size screen will I get if the projector is so far back?

Most front projectors publish 'throw distance' tables that determine how big an image any one projector can produce given a particular distance from the screen.

What display technology does the projector use?

This will allow you to apply all of the information and questions from the previous section.

What is the 'native' resolution of the set and how does it deal with other resolutions?

Most of these are fixed pixel sets, so they must convert all other non-native resolutions to that one. How well is each able to do it? Is it even HD?

Does it have a tuner?

Most front projection systems do not include any tuner, digital or analog. For watching TV, these need a tuner box or VCR to get the signal.

What mounting options are available for both the projector and the screen?

Most projectors can be mounted on the ceiling or placed on a table. Screens can be frame mounted, rolled-up or even stand mounted.