Quick guide to aspect ratio (Stanley posted on May 15th, 2007 )

What is aspect ratio?

The concept is simple enough: aspect ratio is the fractional relation of the width of a video image compared to its height. The two most common aspect ratios in home video are 4:3 (also known as 4×3, 1.33:1, or standard) and 16:9 (16×9, 1.78:1, or wide-screen). All the older TVs and computer monitors you grew up with had the squarish 4:3 shape–only 33 percent wider than it was high. On the other hand, 16:9 is the native aspect ratio of most HDTV programming; it is 78 percent wider than it is tall, or fully one-third wider than 4:3.

At comparable screen sizes, the wide-screen image is a distinct improvement: it offers a larger image, and the horizontal orientation is more akin to how your eyes–next to each other, not on top of one another–view objects.

Both of these formats work perfectly well when they match the TV screen’s native aspect ratio–standard programming on a 4:3 screen (any 1950s to 1990s Nick at Nite fare, for instance) and any newer, wide-screen material on a 16:9 set (HDTV programming or most DVDs). But as soon as you try to watch 4:3 content on a wide-screen monitor or 16:9 content on a 4:3 TV, you need to make some choices as to how you’ll compromise.

 Some critical caveats:

Before we examine the details of those aspect-ratio problems and solutions, it’s important to affirm five key points:

  • Make sure your video settings match your TV’s aspect ratio. Most modern video sources–DVD players, game consoles, satellite and cable boxes, DVRs, and even the video iPod–have an aspect-ratio setting. Make sure you set each device to the setting that matches the TV to which it’s attached: 4:3 for standard TVs, 16:9 for wide-screen monitors (nearly all HDTVs). The one exception is for 4:3 TVs that offer a feature called vertical compression or anamorphic squeeze. Video sources attached to these models should be (counterintuitively) set to 16:9, because they’re designed to display the full vertical resolution of a wide-screen image within the letterboxed area.
  • Make sure your new TV has aspect-ratio control. The next two pages suggest several solutions to common aspect-ratio problems. But they will work only if your TV–or the video source, be it a satellite tuner, cable box, or DVD player–has aspect-ratio control. In general, all wide-screen HDTVs, most HDTV set-top boxes, and a few new 4:3 TVs can control aspect ratio in some way. Many DVD players have Zoom functions, and all can be set to work with both 4:3 and 16:9 TVs, but few have additional aspect-ratio controls.
  • Not every aspect-ratio choice will be available at every resolution. Almost every HDTV has aspect-ratio control, but most sets available today limit the number of choices you have, depending the incoming resolutions. In most cases, you’ll have full aspect-ratio control with 480i and 480p sources (generally standard TV and progressive-scan DVD, respectively), but often you get fewer options, or none at all, for HDTV resolutions (720p, 1080i, or 1080p). Some HDTVs, especially older models, restrict the number of available aspect-ratio choices with 480p sources as well. CNET reviews will always indicate how aspect-ratio control is restricted, so be sure to check when making a purchasing decision.
  • Don’t be thrown off by other wide-screen aspect ratios. When shopping for wide-screen displays–especially flat-panel LCDs–you may see aspect ratios such as 15:9 or 16:10. They are, for all intents and purposes, close enough to 16:9 to be considered synonymous. Unless you’re extremely sensitive to geometry, it’s doubtful you’ll notice the slight stretching or squashing they introduce.
  • Understand native/dot-by-dot mode. Some HDTVs, most commonly 1080p displays, also have an aspect ratio mode that doesn’t scale the incoming signal at all. Often called dot-by-dot or native, this mode simply takes the signal, whatever resolution it is, and displays it regardless of the display’s native resolution. Depending on the signal, this can either fill the screen perfectly, leave black bars on the top or bottom, or leave black bars on all sides. For example, if you have an HDTV with 1080p native resolution and you’re watching a 720p HDTV show, a true dot-by-dot mode will be window-boxed–the 1280×720 program will appear as a rectangle within the 1920×1080 display, surrounded by bars on all sides. (Many dot-by-dot modes only apply to 1080i and 1080p sources, however, so lower-resolution sources like 720p and DVD are still automatically scaled to fill the screen.) Regardless, the true advantage of dot-by-dot is that, with 1080p displays, every pixel of 1080i and 1080p sources is shown on the screen with no overscan and all of the detail promised by the source. The only real disadvantage is that some sources don’t completely fill the screen, so you might see a solid line or interference along the extreme edges of the display. But in general, if you have a 1080p display and are watching 1080i or 1080p sources, dot-by-dot will give you the best picture quality.
  • Burn-in can be caused by black bars. Filling the screen with a moving picture is the safest way to view non-wide-screen content on 16:9 plasma flat-panel and CRT-based rear-projection displays. Leaving the black bars on for an extended period of time can cause permanent damage to the display–often called burn-in or image retention–which often isn’t covered by the warranty. Both plasma and rear-projection CRT sets are particularly vulnerable to burn-in during the first 100 or so hours of use. During that time, we recommend you watch without vertical letterboxing at all, and that you avoid still images, such as paused games or television shows. After this initial period, the danger of burn-in is greatly reduced. Other easy measures to avoid burn in include: find a set or a source that produces gray bars (instead of black) to either side of the 4:3 image and/or features other ways to combat burn-in; turn contrast down to 50 percent or lower; balance your 4:3 viewing with more wide-screen material; in particular, sports and animation make good candidates for stretching. Burn-in does not affect LCD, DLP, or LCoS TVs and is much less likely to affect direct-view tube TVs.

As long as your TV or video source has the proper aspect-ratio control settings, aspect-ratio problems are completely avoidable. Over the next few years, as both hardware manufacturers and broadcasters transition from the older 4:3 format to wider, HDTV-friendly 16:9 wide-screen, aspect-ratio control will be particularly important.

4:3 (standard) TVs

Because they still represent the overwhelming majority of TVs in the marketplace, most television programming is already properly formatted for standard 4:3 TVs. But many movies–on both DVD and cable TV–as well as a small but steadily increasing number of TV shows (for example, Saturday Night Live, ER, Battlestar Galactica and Late Night with Conan O’Brien) are broadcast in wide-screen format. Seen on a 4:3 TV this letterboxing format–named because it duplicates the effect of staring through a mail slot–leaves black bars at the top and bottom of the screen.

Reminder: Before we take a look at the two most common aspect-ratio problems that afflict 4:3 TVs, it’s important to ensure that your video sources (DVD player/recorders, game consoles, satellite and cable boxes, DVRs, video iPods, and so forth) are set to the aspect ratio that matches your TV. Devices connected to standard TVs should be set to 4:3. The one exception is for TVs that offer a feature called vertical compression or anamorphic squeeze. Video sources attached to these models should be (counterintuitively) set to 16:9, because they’re designed to display the full vertical resolution of a wide-screen image within the letterboxed area.

Undesired letterboxing (wide-screen video on a standard screen)

“How do I get rid of those black bars?”
Problem: Black letterbox bars appear at the top and bottom of the screen when watching wide-screen content, such as most DVDs and some network TV shows.
Solution: Use the zoom control on the TV or DVD player to get closer to the image.
Upside: The image will fill the screen, or you’ll see smaller black bars.
Downside: You’ll miss any action on the extreme left and right of the image, which will be cut off. Furthermore, the picture will appear softer because it’s being electronically blown up–just like the muddy images one gets when using the digital zoom function on a digital camera.

TV and video-source aspect ratio don’t match

“Why does everyone on screen look like they’re in an El Greco painting?”
Problem: When playing wide-screen DVDs that are anamorphic (enhanced for 16:9 TVs), everything looks stretched vertically–actors appear taller and thinner than they otherwise would.
Solution: In the setup menu of your DVD player or set-top box, make sure the TV Type (or TV Shape or Aspect Ratio) option is set to 4:3 letterbox or 4:3 pan-and-scan, not 16:9.
Upside: The image will appear in its correct proportions.
Downside: You’ll see black bars above and below the image. However, this is the aspect that the director intended. You may also notice anamorphic downconversion artifacts.
Note: Many newer, more expensive 4:3 TVs–especially HDTVs–have a feature called vertical compression, or anamorphic squeeze. For these TVs, the DVD player’s setting should be switched (counterintuitively, but correctly) to 16:9. As a result, you’ll see a sharper picture with fewer artifacts.

Standard TVs are pretty straightforward, but aspect-ratio issues can get a bit confusing once you upgrade to a set with a 16:9 screen (most HDTVs, for instance). Let’s take a look at how to fix common aspect-ratio problems in the wide-screen world.

16:9 (wide-screen) TVs

The main problem with 4:3 sets is getting the rectangular “peg” of wide-screen programming to fit the squarish “hole” of a standard TV. 16:9 TVs have the opposite problem: decades’ worth of TV programming has been produced to fit the squared-off 4:3 aspect ratio, not the luxuriously wide space of a 16:9 display. There are several solutions, but you’ll need to decide which sacrifices you’re willing to make: deforming the picture, losing a portion of the horizontal image, sacrificing the resolution, or a combination of the three.

Reminder: Before we take a look at the most common aspect-ratio problems that afflict wide-screen TVs, it’s important to ensure that your video sources (DVD player/recorders, game consoles, satellite and cable boxes, DVRs, video iPods, and so forth) are set to the aspect ratio that matches your TV. Devices connected to wide-screen TVs–which include the overwhelming majority of HDTVs–should be set to 16:9.

Vertical letterboxing (a.k.a. pillarboxing)

“How do I get rid of those vertical black bars?”
Problem: There are black (or gray) bars on the left and right sides of the screen when watching standard TV content–any non-HDTV program, for instance.

This problem has three possible solutions. There’s no right answer–just choose the one that’s most visually pleasing to you.
Solution 1: Use the zoom control on the TV, DVD player, or cable/satellite receiver to blow up the image, eliminating (or at least minimizing) the black bars.
Upside: The image will fill the screen.
Downside: You’ll miss any action at the extreme top and bottom of the screen, which will be cut off–bad news if you’re looking at the stock ticker, news crawl, or subtitles. Furthermore, the picture will appear softer because it’s being electronically blown up, just like the muddy images one gets when using the digital zoom function on a digital camera.

Solution 2: Set the TV’s aspect-ratio control to Stretch or Full.
Upside: The image will stretch to fill the screen.
Downside: The black bars are gone, but to fit the square 4:3 image to the wider screen, the picture has been stretched horizontally, making everyone appear squat and bloated.

Solution 3: Set the aspect-ratio control to a nonlinear stretch mode such as Panorama or TheaterWide.
Upside: The image will stretch to fill the screen, but only the extreme left and right will be distorted; anything toward the center of the screen will be displayed close to its proper proportions.
Downside: It’s the happy medium between native 4:3 and stretch, but this mode is implemented in some TVs better than in others. In some cases, panorama mode can be more distracting than pleasing.

Windowboxing

“The film I’m watching on Turner Classic Movies is has black bars on all four sides. How do I fix it?”
Problem: There are black bars on the left and right sides of the screen and at the top and bottom.
Solution: Use the zoom control on the TV, DVD player, or cable/satellite receiver to blow up the image, eliminating the vertical bars and removing (or at least minimizing) the horizontal ones.
Upside: The image will fill more of the screen.
Downside: There’s nothing to miss at the top and bottom of the screen, with the possible exception of subtitles, which may be cut off by zooming. Furthermore, the picture will appear softer.

Undesired letterboxing (“ultra” wide-screen movies on a wide-screen display)

“My favorite DVDs still have letterbox bars at the top and bottom of the screen–wasn’t my new wide-screen TV supposed to eliminate that?”
Problem: There are black bars at the top and bottom of the screen when viewing movies filmed in “ultra” wide-screen formats (wider than 16:9) such as CinemaScope.
Solution: Use the zoom control on the TV, DVD player, or cable/satellite receiver to blow up the image, eliminating (or at least minimizing) the black bars.
Upside: The image will fill the screen.
Downside: You’ll miss any action on the extreme left and right of the image, which will be cut off. The picture will also appear softer.

Take control

Once you get used to viewing movies in their full wide-screen glory, we bet you won’t be able to go back to the cramped confines of a cropped pan-and-scan version. On the flipside, there are still legions of movie lovers–especially those with smaller 4:3 TVs–who can’t stand letterbox bars and prefer to stretch, squeeze, or crop them out of existence. And that’s the beauty of aspect-ratio control: it puts that choice in the hands of the viewer, not of a Hollywood director or network executive. For maximum flexibility, make sure it’s at the top of the list the next time you’re shopping for a TV or home-video peripheral.

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COMMENTS: 2 Comments »

2 Responses

  1. Really thank you for this program. this program is the shortest way to the best performance in the PC World

  2. Mark Deutch says:

    This is a good explanation of aspect ratio, but not how to deal with it in Mediacoder.

    For example, I have 16:9 aspect ratio AVIs (recorded from HDTV) that I’d like to burn to DVD so I can watch them on a standard TV.

    I see that Mediacoder can crop the image. But can it instead add black bars on top and bottom so I end up with 16:9 letterboxed to fit on 4:3?