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In the realm of home theater systems “4K” is what “3D” was five or six years ago, and I mean that in the most pejorative way possible. Sure, 4K doesn’t require goofy spectacles or remind you of cheap 50s cinema gimmicks, and it even sounds sexier than 3D. But I have a hunch most people are confused about 4K and don’t even know it. We’ve reached this ridiculous place where even smart phones are getting 4K displays, and I want to ask you one simple question: Do you know what 4K means?
First, a little clarification: We usually refer to any video with 1920×1080 resolution (or 1080p) as “HD”. This isn’t wrong, but technically video with a lower resolution of 1280×720 (or 720p) is also high definition. Pedants will distinguish a difference between the two by labeling 1080p as “Full HD” (or FHD). For my purposes here, I use the term “HD” exclusively in reference to “Full HD” resolution, 1920×1080.
We’ve all seen the ads. 4K has 4 times the resolution of HD. That’s pretty easy to understand, right? People refer to HD resolution as “1080p” all the time. And 1080*4 = 4,320. That’s probably where the term 4K comes from, right? I mean, 4,320 is just 4K and some change. That makes sense. That’s gotta be what they mean, right?
“1080” refers to the height of the image, which happens to be the shorter dimension for a widescreen television (or movie theater). “4K” on the other hand refers to the (already larger) width of the image. If you look at the actual dimensions of each, 1920 x 1080 and 3840 x 2160, respectively, you might have noticed that 4K video is exactly twice the width and twice the height of HD footage.
Okay, so if it’s only double the size how can anyone claim it is four-times better? I’m glad you asked! 4K does in fact have four-times the resolution (or number of pixels) of HD, but that’s simply what happens when you double the image size.
Take an HD image, 1920px x 1080px ( total resolution = 2,073,600px), and double the height. Now you have an image that’s 1920px x 2160px with a total resolution of 4,147,200px. We’re already at double the resolution of HD, but our image is a weird, slightly tall box. Better double the width to get the proportions back in place. That gives us 3840px x 2160px which adds to a total resolution of 8,294,400px. Voila! Four-times the resolution!
- Can we look at the width of 4K again? 3840px. Three thousand eight hundred forty pixels. I guess it’s 4K sans some change.
- On YouTube 4K is listed as “2160p”.
- Take a look at the blue bars to the right of the yellow (1080/HD) and red (4K/UHD) dimensions. These resolutions are the origins of the terms 2K and 4K. Note that 2K is the same height, but slightly wider than HD. All those theaters across the country that upgraded to 2K projectors are showing you a glorified Blu-Ray stretched onto a massive screen!
- Watch this video about the weird limbo that is the 16:9 aspect ratio
Four-times as many pixels is like, kinda a lot, right? Well, yeah, sorta. It is certainly a jump, but let’s compare it to the monumental leap from SD video to HD. (We could get into some semantics here arguing whether 720 x 480 or 640 x 480 is the proper representation of SD. For simplicity’s sake I’m going to use the 1:1 pixel ratio choice of 640 x 480.)
The resolution of standard definition, or “SD”, footage is 640px x 480px, resulting in a measly total of 307,200 pixels. Note that SD had a 4:3 aspect ratio. HD, as I’ve already mentioned, has a resolution of 1920px x 1080px, resulting in 2,073,600 total pixels and a 16:9 aspect ratio. On top of getting larger, the transition from SD to HD also made the image wider, because of the the switch from a 4:3 to 16:9 aspect ratio. This added even more resolution, 518,400 pixels more to be exact. In the end HD has 6.75-times the resolution of SD. With the way the industry likes to round number we should probably call it an even seven, and seven is quite a bit larger than four.
Beyond resolution SD was also defined by an interlaced analog signal that was designed for old cathode ray tube TVs and monitors. It was just plain ugly. But even when you compare the digital flavor of SD to that of HD you see a massive leap. DVDs were using the old, gross and cumbersome MPEG-2 codec. File sizes were large, and the image quality wasn’t great. It was fairly easy to push past its limits, especially in dark, high contrast scenarios. Blu-Ray disks and HD streaming services pretty much all use the H.264 codec for 1080p video. H.264 is the reason why HD videos on YouTube and all your precious streaming services exist. Heck, it’s the reason your stupid T2i and iPhone can shoot high definition video. The codec combines much higher image quality with much more efficient compression which results in smaller file sizes. We don’t really have anything like that for 4K. Yeah, H.265 has INCREDIBLE potential for a video editor like myself, but for the average consumer, it’s advancements in image quality are likely negligible.
Moving from SD to HD was a total game changer on many levels. The transition from HD to Ultra HD 4K is more like the inevitable, very predictable follow-up to the game changer.
Do you own a 4K TV? Beyond YouTube are you able to find content to watch in 4K?