If you're in the market for a new TV, 4K or UltraHD are two terms you need to know. The next step is figuring out whether you really need 4K, because there's an obvious price difference between the new generation of 4K TVs, and older Full HD models.

Spoiler: No, you don't need 4K.

What Is 4K Or UltraHD?

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Simply put, 4K refers to the resolution of the screen. There is also 8K, which is twice the resolution. Both 4K and 8K fall under the bracket of UltraHD.

The resolution of the more common Full HD TVs is 1920 x 1080 pixels (otherwise known as 1080p, but note that this refers to vertical resolution, while 4k refers to horizontal resolution). In comparison, 4K is 3840 x 2160 pixels, and 8K is 7620 x 4380 pixels.

So, why are 4K TVs a waste of money right now?

You (Probably) Can't See The Difference Between 4K And Full HD

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The big question is whether 4K is actually noticeably better than Full HD. THX, the digital audio and video mastering firm, says the golden number is 55 inches and 6 feet. If your TV is more than 55 inches and you are viewing it from a distance of 6 feet or less, you will actually notice the difference between 4K and Full HD. If not, forget about it.

Our own Matt Smith came to a similar conclusion:

Sit further away, and the benefits are lost; you're unlikely to notice any difference between the two resolutions even if a 1080p television sits side-by-side with a 4K one. I've witnessed this personally, both at trade shows and in stores. HD was an obvious upgrade over what we now called "standard definition" content, but the jump to 4K isn't as obvious.

The bottom line is that the conditions where UltraHD becomes relevant are unrealistic for most homes. A screen in excess of 55 inches with a viewing distance less than 6 feet is highly unlikely. In fact, that's going against the recommended formula to buy a TV for your living room.

If you want to be absolutely sure, try out this 4K calculator to see if you'd benefit from it.

Most Hardware Doesn't Support 4K

All right, let's say you've decided to buy 4K model regardless of the above math. There's a bigger problem: standardization and compatibility.

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H.265 or HEVC: You've probably heard of H.264, the video codec used by most movies and TV shows for streaming on services like Netflix. Well, H.264 isn't good enough for 4K. So a new video codec was announced, H.265 or HEVC (High Efficiency Video Coding). This new codec doubles the data compression, which means it will be easy to stream videos smoothly on existing broadband connections. But there's a catch: the new codec is nowhere close to being widely adopted.

Dan Rayburn, Principal Analyst at market research firm Frost & Sullivan, says HEVC is at least three years away from consumer adoption. Streaming Media blog adds that none of the major players—Adobe, Apple, Google, or Microsoft—have announced HEVC playback support in their players, browsers, or operating systems (both mobile and desktop).

Still, many of the new smart 4K TVs come with a built-in HEVC decoder, so that's good news.

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HDMI 2.0: Good news: 4K connectivity is going to work on HDMI. Bad news: It's a different standard of HDMI. HDMI 2.0 looks like current HDMI 1.2/1.4 and will plug into existing ports too. However, it won't support a full range of features.

HDMI 2.0 can play 4K content at 60 frames per second (fps)–HDMI 1.4 caps it at 30fps. You don't need 60fps for watching most movies, but it's needed while playing video games. And the new PlayStation 4 and the Xbox One consoles don't have HDMI 2.0, so they won't be letting you play 4K games. Some filmmakers are also opting to shoot movies at rates higher than 30fps, like The Hobbit series and the sequels to Avatar.

New TVs come with HDMI 2.0, but most playback devices don't. Some devices released in the last year or two with HDMI 1.4 might be getting a firmware upgrade to HDMI 2.0–check with your manufacturer about this.

Just remember that to take advantage of HDMI 2.0, both devices (input and output) have to support it, not just one or the other.

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Compatibility: Netflix is supporting 4K streaming on some shows like Breaking Bad and House Of Cards. But even then, it's not that simple. Netflix actually needs to certify the TVs before they can stream 4K videos, says Consumer Reports. Amazon Prime Instant Video also has 4K streaming now, but it's unclear whether it requires a similar certification.

For offline viewing, apart from the issues with HDMI 2.0, 4K blu-rays will be coming in late 2015, and you can expect them to cost significantly more because a new standard (HDCP 2.2) is expected to make it harder to pirate 4K videos. In fact, Reviewed.com says 4K content is getting delayed to get ready for these anti-piracy measures. You can also download 4K videos from YouTube, but honestly, those are boring and quite limited.

TVs Are Cheating Your Eyes By "Upscaling"

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Right now, there isn't much content available in 4K. However, if you've got a 4K TV, then the TV has to project in that resolution. So if the source content isn't 4K, what does the TV do? It cheats your eyes.

Several 4K TVs have been known to play with a sharpening effect. 4K content often comes from 2K source footage, and almost always has artificial sharpening effects added — technically a degradation of the original, but a process which adds perceived sharpness. "The sharpening effect would look the same if applied to an HD image instead of a 4k image," writes cinematographer Steve Yedlin.

This is done so that the 4K TV looks better than a Full HD TV in a showroom, when in fact, there is little difference. It's yet another one of those showroom tricks that cost you money.

In a review of a 4K TV, Wall Street Journal noted something similar. They found a strange sharpening effect applied to images, even when sharpness was set to zero. As they put it: "Imagine a TV where every frame you saw was run through one too many Photoshop filters."

You Can't Play 4K Video Games On Next-Gen Consoles

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One of the areas where 4K resolution actually looks noticeably better is gaming. 4K gaming on PCs is stunning despite its flaws. In fact, Matt says he'll move back to lower resolutions only if the frame rate drops below 30FPS (frames per second).

However, that doesn't help gamers who picked up a Sony PlayStation 4 (our review) or a Microsoft Xbox One (our review). Neither of the next-generation consoles will let you play games in 4K resolution, although you can play 4K videos. PS4 went to the extent of clearly stating in its FAQ:

"Support for high-resolution 4K output for still images and movie content is in consideration, but there are no further details to share at this time. PS4 does not currently support 4K output for games."

You Might Need To Upgrade Your Camera Or Phone As Well

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There isn't a large list of smartphones or cameras that can currently record in 4K definition, so there's a good chance you will need to buy a new one. There are about twenty phones on the market, five mirrorless cameras, five video cameras, and five wearable cameras like the GoPro Hero 3 and upwards. Check this list of 4K recording devices, and if your camera or smartphone isn't listed, you'll need to upgrade. The iPhone 6 and iPhone 6 Plus (reviewed by Tim) do not make the cut; but you'll pleased to know the Nexus 6 does.

Summing Up The Case Against 4K

In a nutshell, here's what you need:

  • A 4K smart TV of 55 inches or more, placed at a distance of 6 feet or less, to actually see a difference in image quality.
  • It has to have an HEVC decoder and ideally support for HDMI 2.0 (for gaming and higher FPS movies). And you have to upgrade all your other hardware, which currently doesn't support HEVC, HDMI 2.0 and such.
  • Your TV also needs a secure certificate from Netflix to play approved content - the new Roku TVs have this, for instance.
  • You need new hardware in the near future, like the next generation of video game consoles, since the PS4 and Xbox One you won't be able to play 4K games.

Are you still not convinced? What's your reason for not buying into the 4K fad?

Image credits: Burning dollars Via Shutterstock, Rustyclark, Netflix blog, TRauMa (Wikimedia Commons), Alexey Goral (Wikimedia Commons), scyther5 (Shutterstock), Piotr Adamowicz (Shutterstock)