The Wire, HBO's landmark series about cops, the criminals they pursue, and the whole damn city of Baltimore, is finally in high definition. Reruns of the show in HD will begin on the network on December 26, with digital downloads and a Blu-Ray set to debut next year.

This is great news, right? The Wire is one of the all-time great TV shows, a stunning depiction of an American city in decline pitched somewhere between crusading journalism and socially conscious novel. Getting to see it in the crisp clarity of high-def will definitely add to the experience.

But, see, a lot of Wire fans aren't happy with this release. And the reason has to do with incredibly wonky, but important, aspects of how television is made.

In fact, it all boils down to aspect ratios.

What is an aspect ratio?

The aspect ratio of an image is the ratio of its width to its height. There are a ton of common aspect ratios, but for purposes of this discussion, we're interested in only two. The first is 4:3, and the second is 16:9.

The idea of the aspect ratio is that no matter how large or small you make the image, it will continue to boil down to X units of width to Y units of height. So all 4:3 images will always be four units wide to three units high, while all 16:9 images will be 16 wide to nine high. A 4:3 image is only slightly wider than it is high, while 16:9 is much wider than it is high.

If you divide 4:3 out, you will end up with 1.33 (repeating):1. This is very close to 1.375:1, the former standard Academy ratio for films made in the pre-television era. It's also exactly the same as the aspect ratio for films made in the silent era. This will all be important later. I promise.

What does any of this have to do with The Wire?

The Wire is one of a handful of shows that was produced in the period when television was shifting from standard definition to high definition. Even though most people still had SD televisions, the networks saw that HD was the future and began producing programs in that format, even if they weren't always broadcast as such. This is how, say, HBO could create a high-def Blu-Ray set of The Sopranos, even though that show also bridged the two eras.

As Wire creator David Simon explains in this blog post, The Wire, to keep to a lower budget, filmed in standard definition from its first episode. When its third season began filming, HBO offered the show the chance to update to HD, but the producers declined, wanting to keep the visuals similar throughout.

If this was just a matter of picture quality, that would be one thing. Even those unhappy about the upcoming Wire set are excited to have the show with a clearer picture that will better allow viewers to appreciate the filmmaking.

But think about a standard definition TV and the difference in the shape of the screen compared to a high-def TV. The high-def TV is much wider than it is tall, right? And, as you've probably guessed, that's because an SDTV is in 4:3 aspect ratio, while an HDTV is in 16:9.

Thus, The Wire was shot in 4:3, but it's being blown up to 16:9. And that's inevitably going to mess with the picture's size and shape.

Why?

Think back to the home video era, when most movies were released in so-called "pan and scan" editions that cropped out information from the sides of the picture, in order to have a 16:9 picture fill a 4:3 screen. Cinephiles protested that the hard work of directors deserved to be preserved, even if it meant having those oppressive black bars at the top and bottom of the screen. Having the right information was better than having too little of it.

In the HD era, we very have the opposite problem. Now, we have to expand the image at the sides to fill the screen. And that means we have too much information, rather than too little. So a shot that's carefully composed to, say, function as a medium shot on two people talking alone in a field will suddenly have a whole bunch of the field surrounding them, subtly impacting the visual effect of the scene. And yet because we think our HDTVs have "solved" the old problem of pan-and-scan, a lot of people don't know this. (And, actually, pan-and-scan is still with us, and Netflix does a fair amount of it.)

The reason for this is because there are two different ways to go from 4:3 to 16:9. The first is to simply trim visual information off the top and bottom of the frame, thereby creating a new version of pan-and-scan. But the second (and the one The Wire used most often) is to return to the original video masters — which are often in 16:9 anyway — and turn them into 16:9 shots. But because the images were composed for 4:3, there may be visuals at the edges of the frame that have to be digitally removed. In a period piece, this might include, say, a modern car. Or it could be as simple as a boom mic operator standing just beyond the actors but still in the 16:9 frame. These are often digitally removed, costing time and money.

Particularly in the case of The Wire, where everything was very carefully composed for that 4:3 frame, it can have the effect of taking a show that was often meant to be very close and intimate and making it feel a little too epic. Simon talks at length about some of the shots and how they were affected in his blog post. (Obviously, we won't get a look at this until December 26.)

But so long as the story is the same, does it matter?

Maybe not! Certainly, the writing and performances of The Wire are going to be exactly the same, even with all that added visual information.

But consider this: film is a visual storytelling medium. Throughout any film or TV program, the director is sending you subtle, carefully considered visual cues that affect how you feel about the story. They can create terror. They can send quietly political and social messages. Or they can just make you feel good about what's happening on screen. By failing to preserve the aspect ratio of The Wire (or even offering fans that option), HBO is essentially throwing all of that out.

Why would anyone do this?

In a word, money. For the most part, aspect ratios are some goofy thing that mostly film students know about, which means that when people rent a DVD and find that it has some weird black bars off to the side (or at the top and bottom), they often assume something is wrong with the DVD or their television, rather than assuming that is how the picture is supposed to look. We're used to pictures filling our screens, not seeing them seemingly compressed into a too-small space.

Simon also alludes to this in his blog post. He says those black bars are keeping some people from seeing The Wire. And if that's the case, well, he'd rather they see it than avoid it.

Why doesn't everybody make things in the same aspect ratio?

They actually used to, more or less. As you might recall, the Academy ratio for films (1.375:1) was very close to the ratio for early television (4:3), which meant that TV stations could show lots and lots of old movies to fill time in the day. Go back and look at, say, Casablanca, and it's more squarish than you might expect.

After theater receipts collapsed in the wake of television in the early 1950s, movie theaters began experimenting with wider and wider screens, leading to the development of the 1.85:1 ratio we use today, which is very close to 16:9. Indeed, the top movie of 1952 was something called This Is Cinerama, which was literally just a tech demo showing off wider movie screens.

As movie theater receipts are once again impacted by people staying home to watch stuff on TV, more and more filmmakers are experimenting with images even wider than 1.85:1, or with filming in IMAX, which at 1.43:1 offers an image that is squarer than the typical big-screen release, but still noticeably wider than a standard-def TV. (IMAX, of course, also has that giant, giant screen.)

So we're through the era when television was shot in one ratio and film in another. Instead, basically everything that's made is at 1.85:1 or 16:9, two aspect ratios that work very well together. But don't expect this era to last forever.

Does David Simon approve of the new HD Wire?

Mostly. He and his team went carefully over the show so it would be more or less acceptable. But he's also not praising this upcoming set as the definitive version.

He writes: