This week Sony announced the XBR-84X900, an 84-inch TV with 4K TV resolution. "4K" refers to TV resolution, just as "standard definition" or "HDTV" are TV resolutions. And while 4K is higher resolution than 1080p Full HDTV, it is doubtful that the you or I will be running out to upgrade our TVs anytime soon. Here's why.
When we discuss the quality of the picture on a TV, we often refer to the TV's resolution. A TV picture is made up of pixels on the screen. "Resolution" is the number of pixels on the TV screen. The more pixels on a screen, the smaller the pixels. The smaller the pixels, the better the picture detail. High resolution ("high definition") TVs have more, smaller pixels resulting in smooth, crisp lines around objects. They seem to have better focus and you will be able to distinguish the weave in a person's clothing, stitching on jeans, needles on a pine tree in the background.
If you have a 1080p Full HDTV, it has 1,080 horizontal lines of pixels counted from the top to the bottom of your TV. (For simplicity's sake, let's ignore the "P.") On a 50-inch TV, this pixel count or "resolution" is enough to give you a clear, beautiful picture if you are sitting at least 5 feet away from the TV.
The smaller TVs that we grew up with (often referred to as "legacy TVs") have "standard definition" resolution with 480 lines. At a distance of 6-feet, that gave us a pretty sharp picture because the TV screens are smaller.
If you were to make a 50-inch standard definition TV, the same 480 pixels would have to be bigger than they are on a 27-inch TV in order to fit the bigger screen. When the pixels get bigger, the picture becomes less defined—details are softened and blurrier, edges of objects are jagged.
What is 4K TV Resolution?
A 4K TV refers to a TV that is UHDTV or "Ultra-High Definition TV." But, those wacky electronics people are out to confuse us again!
We refer to standard definition TV as 480 resolution (720 x 480). Full HDTV is called 1080 (1920 x 1080). Notice how the resolution we describe is the 2nd number in the number of pixels. It would stand to reason that 4K is simply four-thousand lines of horizontal resolution counted from top to bottom. But no! On a 4K TV, there are 2,160 lines of horizontal resolution (3860 x 2160).
It's not a direct comparison. Why refer to a resolution differently than we have in the past? The explanations I found offered that 4K doesn't refer to pixel count in the same way as other resolutions. Some techies refer to this resolution as "4K by 2K" which is more accurate. They then shorten it and just say "4K." Others in the tech world say it relates to how you can fit four TVs with 1080 lines of resolution in the space of a 4K TV. This is actually a better explanation for how 4K gets its other name, "Quad Full HD."
Whatever the reason, suffice it to say that a 4K TV has four times the resolution of a 1080p Full HDTV.
Isn't 1080p Full HDTV good enough?
As I mentioned, on a 42, 50, or 60-inch TV, 1080p Full HDTV is enough resolution to create a clear and detailed picture. But what happens when the TV is 84-inches in diameter like the new Sony LCD TV? That's a full 7 feet. The 2 million+ pixels of Full HDTV resolution would become bigger and the picture quality wouldn't be as sharp as it was on the smaller, 42-inch TV. The solution for maintaining high definition quality in TVs over 76 inches is UHDTV or "4K" resolution.
While you might think that 4K would only be suitable for larger TVs, there is a reason that you might want a 50-inch TV with 4K resolution. When watching passive 3D TV (the kind of 3D where you use glasses that don't have power—like those you get at the movie theater), the HDTV resolution is cut in half. Half of the picture goes to the right eye, half goes to the left. So when you are watching 3D the picture resolution is reduced to near standard definition quality picture which has less clarity.
Because of the reduction in image quality in 3D, movie theaters that show 3D movies are mostly using Digital Cinema 4K projectors. The history of 4K originates in the cinema. Likewise, if you don't want to lose quality when watching 3D on your 55-inch TV, 4K can fix the problem. A TV with UHDTV resolution, will deliver Full HDTV quality when the picture is distributed to each eye. 3D movies will be clearer, with more detail.
Few of us will run out to buy a 84-inch TV (as it would take up a wall of a typical living room) unless we have a room dedicated to our home theater. Home Theater 4K projectors have been available for a few years. Sony's VPL VW100ES 4K home theater projector costs in the vicinty of $20,000, so don't expect the 84-inch LCD TV to be much cheaper. Still, I remember the first big screen Mitsubishi DLP TV we sold at the electronics store where I worked. It was $18,000. Within 5 years it was less than $1,500. We'll have to see if all of our TVs will be 4K UHDTVs in the future. Right now, it seems like overkill.