1187: Aspect Ratio

Explain xkcd: It's 'cause you're dumb.
Jump to: navigation, search
Aspect Ratio
I'm always disappointed when 'Anamorphic Widescreen' doesn't refer to a widescreen Animorphs movie.
Title text: I'm always disappointed when 'Anamorphic Widescreen' doesn't refer to a widescreen Animorphs movie.

[edit] Explanation

Aspect ratio is the relationship between the width and height of an image (and in this case, a video) and is denoted in a ratio of <width>:<height> - usually either in lowest common denominator, or with a decimal width to a height of "1". Up until the 1990s, all televisions and most computer monitors (CRT tube and LCD) were in the standard 4:3 aspect ratio, called "fullscreen" (meaning the width is 4/3 or 1.33... times the height). When HDTV was developed, the standard for television screens changed to 16:9 (width being 16/9 or 1.77... times the height), called "widescreen" (although widescreen can also refer to a number of even wider ratios used in feature films). Computer monitors are now available in widescreen ratios, though fullscreen remains common as well.

Letterboxing is a process whereby an image which does not fully fill a screen is expanded to fill the screen by the addition of further material (mattes). Usually this is done with the addition of black bars in the empty space. One example of why this was necessary was widescreen films on VHS cassette. VHS could only record and play back 4:3 images. Thus, in order to display a widescreen film, the rest of the VHS's 4:3 image had to be filled with horizontal black bars at the top and bottom of the image. Those bars were part of the video information recorded on the cassette.

When DVDs were introduced, many DVDs also had letterbox bars on the DVD's full screen image. With the increased popularity of widescreen televisions, DVD players were improved to offer anamorphic widescreen, in which the full widescreen image is horizontally rescaled (shrunk) into a 4:3 size, which the player then was able to display stretched horizontally back to the proper widescreen aspect.

With the advent of Blu-ray, video is generally encoded in whatever its proper aspect ratio is intended to be, and the player itself is left to appropriately matte the image.

The problem with letterboxed video (such as a 16:9 video letterboxed for 4:3) is that if one tries to watch the video on a 16:9 widescreen, where the image should fill the whole screen, instead the 4:3 letterboxed image fills part of the screen with further vertical mattes on the left and right of the image, thus producing an image much smaller than it needs to be, with mattes on all four sides. Some TVs or media players can zoom to help resolve the issue, although the video resolution usually suffers. By encoding only the video itself and allowing the player to do the matting, the video can be seen as large as possible on any given screen.

Animorphs is a late-90's to early-00's young adult book series about shape-shifting teens who turn into animals to fight body-snatching aliens. Sony held the rights to create a film, but never made use of them, beyond creating URLs for a proposed movie on December 11, 2012. Animorphs has since been mentioned in the title text of 1360: Old Files as well as being the main joke in 1380: Manual for Civilization and 1817: Incognito Mode.

In this comic, Randall appears to be complaining about the issue of widescreen videos which have been rescaled to 4:3 by "squashing" the video horizontally to make it narrower, and in the process causing everything to appear thinner/taller than it really is. This is akin to the car crushing Randall depicts in the comic.

A note is that, if someone managed to "expand" the car, the car would not be "un-crushed" and probably even weakened even more, referencing the bigger damage done when "squashed" video is attempted to be "expanded" to its original ratio, distorting the video quality.

[edit] Transcript

[A car is crushed in a large black clamp.]
Whenever someone uploads a letterboxed 16:9 video rescaled to 4:3, I do this to their car.

comment.png add a comment! ⋅ comment.png add a topic (use sparingly)! ⋅ Icons-mini-action refresh blue.gif refresh comments!


Oh man, I haven't read Animorphs since I was a pre-teen. That takes me back. The aspect-ratio joke made me giggle mildly, but that was secondary to me. 06:10, 18 March 2013 (UTC) - The problem I see here is that the vertical black bars are pillarbox and not letterbox. How did Randall manage to goof on this? Cybertronic (talk) 06:25, 18 March 2013 (UTC)

"causing the image to be horizontally squeezed and including the matte bars." I'd like elaboration on this bi, I'm not quite sure what's being said... Though it sounds like it'd appease Cybertronic's complaint. - Zergling_man 07:11, 18 March 2013 (UTC)

Hey, uhm, I'm not familiar with the format I'm supposed to use here or anywhere, but I'd like to point out that in the comic image, it looks like that car is being transformed from a 16:9 format to a 4:3 format, and the black poles on the ends are like the black parts a widescreen user would get while watching a 4:3 video. -- ‎ (talk) (please sign your comments with ~~~~)

Yeah, I got the impression this had to do with the 'Postage Stamp' problem. Something that was originally made in widescreen is converted to 4:3 using a 'hard matte' process: it's actually converted into a 4:3 signal, and the black bars are part of the signal. This contrasts with the 'anamorphic widescreen' process, where the full widescreen signal is included, without the black matte bars, which are added by the television if needed, and only if needed. An anamorphic widescreen video would show up on a 4:3 television letterboxed, with the black matte bars on top and bottom: on a widescreen television, it would instead fill the TV, assuming the aspect ratio was the same
A hard matted letterbox, on the other hand, shows up the same on a 4:3 television as the anamorphic would, but when shown on a widescreen television, is still shown in 4:3, with additional matte bars (black or grey) on the sides, in addition to the 'hard' mattes on top and bottom. This leaves your widescreen television showing a widescreen signal at only a fraction of the television's full size, with most of the screen wasted on needless matte bars. -Graptor 22:29, 18 March 2013 (UTC)
Having thought about it a bit while microwaving dinner, I thought of another explanation that makes more sense, and I can recall seeing this one on youtube. Rather than just adding matte bars to the top and bottom to the original 16:9 video to make it fit in 4:3... they actually rescale it to 4:3. This compresses the horizontal axis and makes everything look a bit squeezed. In numerical terms, you'd be taking, say, a 1920x1080 video, and crushing it down to 1436x1080, and not by chopping the sides off. You just compress the whole image down to fit, and the end result looks terrible. Like the car. -Graptor 22:48, 18 March 2013 (UTC)

I'm new to this wiki editing. Love this site; love XKCDs comics. I believe that there is a typo in the description, "...denoted in a radio of..." should be "...denoted in a ratio of...". { -- (talk) (please sign your comments with ~~~~)

Quibble: I'm pretty sure that the term "fullscreen" as a description for a 4:3 aspect-ratio screen is a rarely-used back-formation. It was originally a marketing term for video sources (such as a recording of a movie), coined to describe wider-ratio films that had been chopped, compressed, or otherwise modified to fit on a 4:3 TV without letterboxing, thus filling the full screen. My impression was that it was partly about having a succinct label (to differentiate from letterboxed videos); partly about trying to disempower cinephiles and movie reviewers, who generally lambasted studios for releasing a different version to home video than had been shown in the theater; and partly about newspeak, trying to obscure the fact that it was in fact letterboxing that gave you the whole film by pretending that you were getting "more movie" with fullscreen versions. I'd never heard the term "fullscreen" used to describe a physical screen, only its use, prior to this explanation. Wikipedia/wiktionary seem to concur that using it to describe the physical screen is a new thing (based on its absence in the wiktionary entry, and existing only as a redirect in wikipedia). 22:41, 20 March 2013 (UTC)

It's not so much a back-formation I think, as an incorrect, semi-logical extension of prior terminology. Most people's experience with the terms 'fullscreen' and 'widescreen' in this context is, as you note, on commercial movie releases. Back in the olden days, when all pretty much were 4:3 (with the occasional rare 5:4 model), and VHS ruled the market, it was not uncommon at all for movies to be released in two formats: a letterboxed format preserving the original aspect ratio via matte bars, nigh-universally labeled 'Widescreen'; and a Pan-and-Scan (that's the technical term) version filling the entire screen by chopping parts of the image off, generally either unlabelled (as it this was considered the 'normal' format at the time) or labeled 'Fullscreen' (as it filled the entire screen). Originally the 'Widescreen' releases were semi-rare, as the general perception was that people didn't LIKE those black bars at the top and bottom of the screen (and indeed, some people quite vehemently hated them). They grew in popularity and got more common as time went on, which was probably one of the reasons why flat panel televisions ended up being 16:9 rather than 4:3 when they appeared. The twin releases continued, however, as a lot of people still had 4:3 televisions, and some of them still really hated letterboxing. Even after DVDs showed up, this continued, with the Pan and Scan release more and more commonly being labeled (almost always as 'fullscreen').
If I had to guess, someone that didn't know the proper terminology, having observed that 16:9 televisions were commonly referred to as 'Widescreen', the same as on the movies they've bought or seen in stores, might assume thusly that the terminology would ALSO match when talking about a 4:3 television. This would be reinforced by the fact that an old 'fullscreen' video/DVD, labeled as such, would show up on a widescreen television as a 4:3 image with matte bars on either side. So they conclude that 'fullscreen' equals '4:3 screen ratio', when it's really just an outdated expression from a bygone age. -Graptor 23:53, 21 March 2013 (UTC)

Oh, and others are correct: the comic very specifically refers to "rescaled" video--that is, in fact, the practice of distorting the video to the new aspect ratio, and not adding matting bars on any side. It used to be actually done--though I've never seen it for a whole movie, only select scenes in a movie--and it's horrible. 22:46, 20 March 2013 (UTC)

The word "letterbox" in the caption is inaccurate and unnecessary to the joke. If the offensive video started off as letterboxed (i.e. black bands on top and bottom) it would already be in a 4:3 ratio (the wide-aspect picture plus the letterbox bands would total out to a 4:3 picture). The scene depicted in the cartoon is analogous to taking content with a 16:9 raster, squeezing it to fit in a 4:3 frame without letter-boxing, and then displaying it in a 16:9 frame (i.e. pillarboxing). I see this on YouTube frequently, but I don't know if that's because YouTube is doing something wrong automatically or the people uploading are doing something wrong.In the end, the Randall's objection has much more to do with the unnatural distortion than the "boxing". (NOTE: edited this comment since I first posted it earlier today because I got it substantially wrong back then...) somebody

Personal tools


It seems you are using noscript, which is stopping our project wonderful ads from working. Explain xkcd uses ads to pay for bandwidth, and we manually approve all our advertisers, and our ads are restricted to unobtrusive images and slow animated GIFs. If you found this site helpful, please consider whitelisting us.

Want to advertise with us, or donate to us with Paypal?