Hey, did you know 4K often isn't actually 4K?
What? Even though tons of electronics companies advertise screens, game consoles, and streaming sticks
with 4K support, there's actually no real standard for what the heck 4K really means.
It's just a word. It's just made up. You see, 4K is called 4K because it refers to resolutions that are approximately 4,000
pixels across. The most common resolution that's advertised as 4K is 3,840 pixels horizontally by 2,160
pixels vertically, which is what you typically see on TVs and computer monitors, often marketed
as Ultra HD or UHD.
And so this resolution isn't quite 4,000 pixels across, but the 4K used in movie production,
called DCI 4K, measures 4,096 by 2,160.
So the aspect ratio is about 1.9 to 1, a little wider than the typical 1.78 to 1 we're used
to on TVs and your typical computer monitor. You might know that aspect ratio by its other name, 16x9.
But DCI 4K isn't the only movie 4K, as it's primarily used for shooting the film.
By the time you get to the movie theater, though, you're probably seeing the film in
Cinemascope 4K. This sounds awfully fancy, but the actual resolution is only 4,096 by 1,716.
And while that produces the 2.39 to 1 aspect ratio that looks cinematic, a typical 4K display
at home has over one and a quarter million more pixels.
So don't be fooled into thinking you're supposed to be seeing the latest blockbuster
in some kind of mind-blowing detail, you're mostly just cutting off the top and bottom.
To further illustrate this point, some products cut down resolution even further to get that
cinematic, widescreen look. Sony's line of Xperia phones are known for this with their trademark Cinemawide 4K displays.
But Cinemawide is actually just a cut down version of Garden Variety UHD, with a resolution
of 3840x1644 to achieve a more theatrical 21x9 aspect ratio similar to many ultra-wide
monitors. We're not trying to say these displays are bad, as they're still good looking OLED screens
with HDR support, just don't expect more pixels than you'd get on a $300 TV.
This illustrates why 2160p isn't an exact synonym for 4K, even though many people might
want to call it that since we often refer to HD by its vertical resolution 1080p.
We've already covered two resolutions marketed as 4K, with vertical resolutions falling
well short of 2160 pixels, and on the other side of that coin, there are products like
dashcams advertised as 4K because they're 2160p, but less than 3000 pixels across, producing
a more square looking video that isn't really close to what we typically think of as 4K.
So the use of terms like 1080p and 2160p to describe resolution actually go back to the
age of CRT displays. We know those big, heavy TVs and monitors we used until the late 2000s and are still
used today at really cool Super Smash Bros. tournaments.
CRTs didn't have pixels in the sense that we think of them today, rather they generated
horizontal lines that contained analog data, which varied as you went across the screen.
In other words, they had a vertical resolution, but not a horizontal one.
This is why the industry used terms like 480i or 576i to describe TV signals back when
CRTs ruled the world, with the i standing for interlaced, meaning that a CRT would only
scan half the lines of a frame at once to save bandwidth.
By contrast, the P in 1080p stands for progressive, meaning the monitor scans the whole frame
all at once. But even though modern LCD displays have a defined horizontal and vertical resolution,
the practice of using a single 3 or 4 digit number to represent the entire resolution
stuck around. But even if a product clearly states both its horizontal and vertical resolution, you
really need both that information and the size of the display to get across how much
detail it can convey, since a 4K resolution doesn't really mean much if you're sitting
two feet away from a 200 inch screen.
Which is why the 8K TVs on the market are mostly really big.
So isn't there a better way than 2160p to describe how much detail a display can show?
Yeah, it turns out that there is, indeed. It's a spec called pixels per inch, or PPI, which is just what it sounds like, the number
of pixels in a one inch line. PPI, combined with aspect ratio, gives you a really good idea of what the actual visual
experience will be like, and this system is used by none other than Apple, who uses it
as the basis for the retina display marketing. Wow, they were actually right about something all along.
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