As 4K displays are now coming out, a common debate between people online has been about the benefits of 4K compared to HD in a normal viewing environment. Many people will say that 4K looks amazingly sharp and it's impossible not to see the difference, but many others will say that in a regular living room, with a regular sized screen, you really won't see much of a difference.
Update July 3rd, 2013: Read more about HiDPI and 4K Display use cases and benefits. My new article compares smartphones, tablets, laptops, monitors, TVs, and projectors to see where high-resolution provides the most visible benefit.
December 1, 2014: Revised text as 4K/UHD TVs are now available everywhere
November 27, 2015: Updated links and comparisons
October 22, 2017: Updated for current status of 4K displays
4K In The Store
Most people who have seen 4K to this point see it at stores that have dedicated displays for it, and not at home. Many times these are set up to only allow you to be so far away from the screen, which makes 4K look great, as it really does look amazing from 3' away. They also use special content to show off 4K, since streaming content from Netflix or Amazon in a store is unreliable. When standing only a few feet away from a giant TV watching custom demo content, usually with beautiful landscape shots and not fast action sequences, there is no doubt that 4K content looks amazing.
Now if you were to get that same landscape shot in 1080p next to the 4K version and sit as far away as you do in your living room, you might see a different image. The 4K version has a good chance of looking sharper, it’s all about size and distance, but it might not be as large a difference as you expect. There is also a chance that the 1080p will look better since more pixels don’t make an image automatically better.
Better Pixels, not More Pixels
While almost every TV out there today is 4K, not every 4K pixel is made the same. There are a few features on TVs that can make certain 4K displays look better than others that you need to watch out for.
High Dynamic Range: HDR, or High Dynamic Range, allows a TV to have highlights that are 5-20x brighter than they have been in the past. This allows for images that are much more life-like than they have been before. Reflections of the sun off of water or metal, along with bright highlights look far more realistic than ever before and create a better image on your TV. While all HDR content is currently 4K, it’s a separate feature that not all 4K displays support. There is also another major flaw in that TV companies will market their TVs as being “HDR” because they can read the HDR data, even if they can’t display it. It’s important to read reviews of HDR TVs to see how many nits (or cd/m2) they can display. Anything around 300 won’t look different than an SDR (standard dynamic range) TV. Something that does 500-600 will make an impact, and a much larger impact if it’s an OLED with infinite contrast ratios. The best TVs can do close to 2000 nits and will make HDR truly look like it should.
Wide Color Gamut: HDR content also supports wide color gamut, or WCG. Previously TVs could only show a certain range of colors, but newer WCG compatible TVs can show even more. Blues, Reds, and Greens can look more realistic than ever before on your TV screen, and shades that were never possible before will now be there to see. Combined with HDR, you also get these colors to be visible when very bright, whereas before bright colors tended to turn white on TVs because they couldn’t display them. Unlike extra pixels, extra colors are something that you can see no matter how close or far you are sitting from the screen.
Dynamic Backlight: Since most TVs are still LCDs, they need a dynamic backlight to produce better contrast ratios. By lowering and raising the level of the light behind the LCD panel, you can make shadows darker and highlights brighter while still keeping details there. The best TVs will talk about how many backlighting zones they have, with more almost always being better. The Vizio M-Series has 32 in 2017, while the TCL P607 offers 72. The Sony Z9D, probably the best LCD TV on the market, has around 650 zones. You also can’t do HDR on an LCD TV correctly without a dynamic backlight. Some LCD TVs still don’t have them, so for the best image quality, you need to look for a backlight (full array backlights are better than edge lit as well).
If you choose to go with an OLED display, you don’t need to worry about this. Since each OLED pixel makes its own light, there is no need for a backlight to produce the best images with the highest contrast ratios. An OLED cannot get as bright as a Sony Z9D, but it can get darker. OLEDs are at their best in a darker home theater room, while a brighter LCD might be preferred in a room with lots of windows.
Is the Content there?
Even if you have a new 4K TV that does HDR and WCG well, it might not matter if you don’t watch programs that support it. Broadcast TV is almost entirely in 1080i or 720p, without wide color gamut or HDR, except for a few special satellite broadcasts. While upgraded TV broadcasts are going to come in the future, and demos I have seen look fantastic, they aren’t there today. And it probably is a few years off as well. Current TV doesn’t benefit from any of these features.
If you rent or buy your movies on disc, they might not benefit as well. The only way to get the benefits of 4K with HDR and WCG is from buying movies on 4K UltraHD Blu-ray discs, which cost around $30 each and require a new player. We have an extensive guide to these discs, and review as many as possible, but it still requires you buying all new material to watch. The large DVD and Blu-ray libraries people have built up over the past two decades won’t benefit at all from these new technologies.
If you stream content, you might be better off. Netflix and Amazon are constantly adding new content that uses 4K resolution with HDR and WCG. Shows like Narcos, Stranger Things, Mindhunter, The Man in the High Castle, Chef’s Table, and more take full advantage of these new TVs and look fantastic when showing content. Movies are sometimes in 4K but not usually with HDR or WCG, but the original content is.
AppleTV 4K owners also benefit since their older titles will be upgraded to 4K when they are available from iTunes. Using Movies Anywhere, we’ve watched lots of our existing digital copies get free upgrades to 4K versions with HDR and WCG and they look fantastic. Most movies don’t have 4K versions available yet, but it is mostly a matter of time. Seeing how great older titles like Blade Runner can look when given a new 4K version make you realize that even your favorite films from 30+ years ago can still look better at home.
2K DIs: The dirty secret
One thing people don’t realize about 4K as well is that most Hollywood content today is only 2K. When they edit a movie in Hollywood, they do so using a digital intermediate. On this DI, they do all the special effects, color correction, and final editing. In almost all cases they do it at 2K resolution because either they haven’t upgraded their systems to support 4K, or it would be too expensive or time-consuming. Special effects, in particular, take much longer to do at 4K resolution so they almost never are done this way.
This means that even films that use 4K, 6K, or even 8K cameras often produce a finished product at 2K resolution. The image will be sharp and free of artifacts thanks to the higher resolution in the capture, but when you get it at the end everything is done at 2K resolution. 4K discs of these movies, including huge titles like Guardians of the Galaxy 2 and Wonder Woman, are only upscaling 2K images to 4K resolution on the disc.
The good news is that these movies also have HDR and WCG, which make more of an impact than the extra resolution does. The problem is that if you have a TV that is only 4K but can’t show HDR and WCG correctly if at all, you aren’t getting any benefit from your 4K TV. The image would be almost identical when looking at a 4K UHD disc, where a 2K DI is scaled, or a Blu-ray disc, where the TV does the scaling. There might be some small differences, but nothing to make the price difference or upgrade worth it.
Look for other specs, not 4K
The key with 4K TVs is to look at the other specs, not the resolution. A 4K TV that can’t do WCG or HDR, or lacking local dimming, isn’t worth upgrading to. If you watch content that benefits from HDR or WCG, then a new 4K TV that can support these features will show you a better picture than you’ve seen before.
Of course, going with an OLED TV will also improve everything you watch, since they have better contrast ratios than any LCD TV and better viewing angles. They aren’t always ideal for a bright living room but for a darker room we feel they offer the best image quality you can get today with almost all content. If you watch exclusively HDR content then an LCD like the Sony Z9D, X940E, or X930E can show better highlight detail than an OLED, but with non-HDR content won’t offer the same level of performance in our experience. But for a living room, especially if we get HDR sports using HLG in the near future, they can be a great choice.
There is a chart from Carlton Bale available that shows when you might be able to see the difference with 4K compared to 1080p or 720p, but I decided to make my own 4K calculator that gives you just a little more detail. Using this you can enter your screen size, your distance from the screen, and your vision to generate some numbers for you. The information this will provide you is:
- The Pixels Per Inch for 480p, 1080p, and 4K signals based on the screen size.
- The maximum resolution that you can discern with your vision based on the distance from the display
- The ideal 4K screen size for your distance, which is the smallest screen at which point you can resolve all the pixels
- The ideal distance from a 4K display of your specified size, which is how close you need to sit to resolve every pixel
- The amount of extra resolution that would be visible on a 4K display compared to a 1080p display based on your screen size and distance. The maximum amount would be 300%, and the minimum is 0%
I've also created a chart, seen below, that gives you a quick glance to see what the ideal viewing distance is for a 16:9 display based on size and resolution. This is based on 20/20 vision, and the viewing range for each resolution is the distance you can sit from that TV and see more detail than a lower resolution, and are not close enough to see the extra detail in a higher resolution screen. So with a 50" 1080p display, if you are closer than 9'9" you will see more detail than a 720p display, but if you are more than 6'6" away, you couldn't see any more detail on a 4K display.
This calculator does make assumptions about vision and arc minutes, but those that I talked to said this was as good of an assumption to make for human vision as anything else. If you think that it is off, you can easily adjust the vision to 20/15 or 20/10 to make it more accurate to you. This also will let you calculate for devices like cell phones and tablets, that will often be placed much closer to your face, to compare them to a 4K display that is much further away. One more assumption is that you have a 16x9 screen, though other screen ratios may be supported in the future.
Many reviewers have tried to compare 4K to 1080p to see if they notice a difference. David Katzmaier pulled in a panel and showed them the same content on 4K streaming from Netflix and 1080p Blu-ray and none of the people could pick out the 4K display. At the same time, HDTVTest did a similar test using 1080p compared to 4K, but they used their own custom content instead of streaming content. In their testing people do notice the difference from a reasonable distance, though unless you are shooting you own 4K content you can't test this yourself.
I talked to other reviewers who tested projectors, being able to instantly switch between a Sony 4K projector and a JVC X700R on a 120" screen. They could barely notice the difference with the 4K resolution using content directly from a RED 4K camera. Even when they did notice, they preferred the JVC image because it had better blacks and a better contrast ratio, and the eye notices that more than resolution. With any display, resolution is only a single factor in how good a display looks. Knowing how much you might see that increased resolution can help you decide what TV will best work for you.
Hopefully this will help you to determine if you will see much benefit from 4K in your situation, as well as making it easier to compare devices like a cell phone or tablet that you hold very close to your face to a TV that likely sits across the room from you.