Stephan Jukic – June 28, 2016
One subject that comes up very often in discussion and comments about 4K TV displays is the question of their refresh rate. The reasons for this are pretty straightforward. One the one hand, refresh rate sped is an important part of how well movies and other content on your TV display and especially how well content displays if it comes with fast paced motion sequences (as is the case for most popular home entertainment content.
On the other hand, the TV manufacturers themselves have themselves added a whole pile of confusion to the 4K TV refresh rate mix by throwing around all kinds of specific jargon to describe their own TVs’ respective refresh rates. What’s worst about their tactics is the fact that a lot of what they say is either vaguely dishonest or outright false in some cases, and only serves to confuse consumers more instead of helping them out.
This is where this post comes in. We’re about to cut through all the jargon, misleading marketing terminology and confusion in general to lay down for all you readers the three core things you need to know about refresh rate: What it really is as far as content is concerned, what the native and “enhanced” refresh rates of the major 4K TV brands are and what the mix of both these first two things really means for real display performance
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All premium modern 4K TVs, such as this Samsung KS9500, come with native refresh rates of 120Hz
What is 4K TV refresh rate, really?
At its most fundamental level, refresh rate is exactly what its name indicates. It’s the rate at which your TV display refreshes the picture in a single second. The higher this number goes, the more likely you are to have a smooth, natural looking and fluid picture quality, especially for fast paced content and even more particularly for fast paced high resolution content like that which you’re going to be watching on your 4K TV. However, there is a sort of variable upper limit at work to just how much this content can be enhanced by a higher refresh rate and this upper limit is a bit content dependent (more on this shortly).
You see, when it comes to the video presented on your 4K TV’s screen, details beyond those already in the source video itself can’t actually be added to the picture by the TV display itself. Furthermore, for the vast majority of native 4K and other movie, TV show and streamed sports or documentary content you’re going to watch on your 4K TV from any source, HD or 4K, the actual refresh rate of the source footage itself is never going to be greater than 60Hz, at last so far as far as content transmission technology is concerned.
With some footage, especially movie content from film reel sources, the frame rate equivalent of refresh rate might even be 24 frames per second, which are upconverted to 30fps for TV viewing and then shuffled around in certain ways so that they display at the equivalent of a 60fps frame rate that will match the 60Hz refresh of most digital content.
4K TVs on the other hand offer actual, totally real native refresh rates that in the vast majority of cases are either set at 60Hz or 120Hz (60 or 120 images, or frames per second in essence). With older HD TVs, the common refresh rate tended more towards 60Hz or less (with many models offering 50Hz real refresh rates) but because 4K TVs are widely considered to be a sort of premium home entertainment technology, 60Hz quickly became the hallmark of only the more economical or smaller ultra HD models and pretty much all premium 4K TVs from every major brand now offer native 120Hz refresh.
How does native refresh rate mesh with content frame rates?
This of course begs the question: How does a native 120Hz refresh rate mesh with content that only presents at 60Hz or possibly even a lower frame rate? Well, quite simply, even at their native refresh rate, most 4K TVs take 60Hz video and then sort of “enhance” it by two different means, both of which are commonly used depending on which TV model one is viewing.
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Frame Interpolation at work
The first of these methods is called frame interpolation, and it is a technology run by your 4K TV’s processing engine by which two or more different real content frames are blended together by the TV to create a sort of falls intermediate frame between the real ones, which essentially fools a viewer’s mind into seeing a smoother sort of picture. In 120Hz 4K TVs, this technology is very common and it usually works at its best in higher quality models.
The next possible method of frame rate enhancement is called black frame-insertion (BFI for short) and it works by shutting off all or part of a TV’s backlight rapidly during the extremely brief moments between frames and thus producing what are essentially dark TV-generated frames between real content frames. This may seem like an odd sort of method for making a picture seem smoother but it works at reducing motion blur because it essentially tricks the mind in how it views image transitions during the flow of content frames, as we’ll describe in slightly more detail by going a bit into what is called motion blur.
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Black frame insertion, in this case from an Eizo monitor but with the same principle at work as in 4K TV displays
What about Motion Blur and Judder in 4K TVs?
Motion blur is the content display problem both of the above motion control technologies are designed to avoid in both 120Hz and 60Hz 4K TV models. It should however be noted that 4K TVs with native 120Hz refresh usually deliver their motion control tricks better than their 60Hz counterparts. In either case, motion blur as we viewers perceive it is in fact a blend of different factors. First, there is the electronic blur crated by the frame transitions on your TV screen as it handles 60fps or lesser content. Secondly, a large part of motion blur is also caused by our own mind noticing frame motion in content and then subconsciously making assumptions about where moving objects in an image will go next. Third, and least manageable is the motion blur caused by the original cameras as they filmed a piece of content during fast movement.
While your 4K TV can’t really do much about camera generated motion blur in a piece of video, the technologies described in the sub-section above (frame interpolation and BFI) are designed to handle the first two causes of motion blur. Both trick our brains into making fewer assumptions about content movement and as a result we see less motion blur between frames as objects move in a movie or sportscast and so on.
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The better a 4K TV is at delivering its native refresh rate of either 60Hz or, more commonly, 120Hz and meshing that refresh rate with the actual frame rates of 24p, 30fps or 60fps content (60Hz content) from a video source, the more naturally smooth your image will look. This will of course mean less image flicker, less judder and of course, less motion blur. Judder in particular can be problematic for many ultra HD TVs when they play 24p content that has to be heavily processed to render on a 60Hz or 120Hz TV display (and at 3840 x 2160 pixels no less!) and one of the key differences between high quality 4K TV models with excellent motion processing engines and their cheaper, less effective counterparts is seen in how much better the former deliver judder-free movie content than the latter.
Great examples of 4K models with 120Hz refresh and superb judder management capacity for movies are premium TVs like the Samsung 2015 and 2016 SUHD models and LG’s OLED 4K TVs from this year or last year. Sony and Vizio premium TVs are also generally excellent at handling motion blur and judder.
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What about refresh rate and PC gaming?
While all video entertainment content for your 4K TV will fed into the television at 60Hz or less in terms of frame rate, 4K TVs today are also very often used as powerful and gigantic 4K PC monitors through their HDMI cables. This opens these TVs up to use as displays for high frame rate HD gaming and for 4K gaming as well (if your PC has a powerful enough GPU running inside it).
What makes most modern (2015 and 2016) 4K TVs particularly great as PC monitors is the fact that their refresh rates can often support two different things. On the one hand, all of the major brand’s 4K TVs of 2015 and 2016 will allow for 4K UHD gaming at a solid 60fps due to their nearly across the board support for 4k signal connectivity @ 60 hz and at chroma 4:4:4 sampling. And on the other hand, a large number of this or last year’s 4K TV models (but not all) also support Full HD gamming at 120Hz due to their native 120Hz refresh rate processing capacities.
Great examples of 4K TVs for 4K PC gaming at 60Hz and with chroma 4:4:4 include the Samsung JU7100, LG OLED 4K EF9500, Samsung’s 2016 SUHD KS8000 (or KS9000 and KS8500 and other KS-Series SUHD models) and more budget oriented TVs like Vizio’s P-Series 2016 models. 4K TVs with Full HD support at 120Hz for PC gaming use include the highly affordable Sony X810C and the X850C as well.
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So what do all those enhanced frame rates in 4K TVs mean?
Now, before we go further, remember this one fundamental and simple point to avoid any confusion that might result from any so-called refresh rate beyond 120Hz: In the current 4K TV market, pretty much all models, from the cheapest to the absolutely most expensive 2016 LG OLED 4K TVs like the G6 offer actual native refresh rates of either 50Hz (quite uncommon with newer 4K TVs) 60Hz or 120Hz.
Any refresh rate number stated by a manufacturer that goes beyond 120Hz is essentially not real. Instead, it depends on even more intensified versions of technologies like frame rate interpolation, black frame insertion and backlight scanning. These enhanced refresh rates typically range from 120Hz to 240Hz and are found in the 4K TV models of all the major manufacturers, each enhanced frame rate going by a different name, though they all do the same basic thing, which is to even further smooth out motion blur, judder issues and in general maintain smoother motion control when displaying either native 4K video content or non-4K video and gaming sources of entertainment on a TV screen.
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As we’d said, the major brands all have their own names for all these “enhanced” artificial refresh rates and their numerical frequencies can also vary slightly. However, for the most part they are double the TV’s true native refresh rate.
Thus, if a 4K TV offers a native refresh rate of 60Hz, it will have an enhanced motion processing rate of 120Hz, and a native 120Hz 4K TV will offer enhanced motion processing of 240Hz. Examples of these enhanced rates and their specific names include the following, by major TV brand and specific enhancement name for 2015 and 2016:
- Sony: MotionFlow
- 120Hz for 60Hz native refresh and 240Hz for 120Hz native refresh
- Samsung: Motion Rate
- 120Hz for 60Hz native refresh and 240Hz for 120Hz native refresh
- LG: TruMotion
- 120Hz for 60Hz native refresh and 240Hz for 120Hz native refresh
- Vizio: “Effective Refresh Rate”
- 120Hz for 60Hz native refresh and 240Hz for 120Hz native refresh
- Vizio also offers a so-called “Clear Action” rate that’s twice even the reprocessed “Effective refresh rate”, with values like 480Hz and 720Hz for native 60Hz content and 960Hz for native 120Hz displays. These numbers are meaningless and simply exist to impress potential buyers with their size. Effective refresh rate and native refresh rate are what actually matters in Vizio 4K TVs.
- Panasonic: Image Motion
- 120Hz for 60Hz native refresh and 240Hz for 120Hz native refresh
A note on grossly exaggerated motion enhancement rates
One final note about the enhanced motion processing technologies of these major 4K TV brands is that they do in fact reprocess native video quality in ways that change its nature, so whether they actually help IMPROVE picture quality or not (more on this next) they can at least be said to do something to how content on your TV visibly displays.
Previously, many 4K TV brands included even more ridiculously high supposed content refresh rate enhancements that would reach up beyond 240Hz to levels like 480Hz, 600Hz, 720Hz and even 960Hz or more. These are possibly some of the most confusing numbers of all too many consumers and what’s worst about them is that they’re in essence completely arbitrary, added in and taken to extreme degrees more for the sake of impressing consumers with big numbers than for actually offering real content improvements.
Luckily, this has become less of a TV maker trend since 2015, as consumers become savvier and professional reviewers more often slam these TV makers for being disingenuous with these arbitrary numbers. On exception is Vizio, as we’ve noted above. They first offer their “effective refresh rate”, which is twice the actual native refresh rate and a valid measure of motion reprocessing, and then can’t seem to help themselves from also adding in the completely arbitrary “Clear Action” rates of 480, 720 or even 960Hz for even their 2016 4K TVs. This is a shame since these television models are genuinely great at 4K content rendering and display, without any of the silly “Clear Action” hype having to even be mentioned.
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Graphics like this example fool buyers into thinking that refresh rates beyond 240Hz exist in today’s 4K TVs. They do not and the stated rates beyond 240Hz do nothing for image quality.
Are these “enhanced” refresh rates worth the hype?
In very simple terms, since even the native refresh rates of today’s 4K UHD TVs often mean reprocessing actual content refresh/frame rates for the sake of reduced motion blur, most of the motion enhancement technologies we mention above don’t really do much for the stuff you view on your TV and for watching movies, TV shows and even sportscasts, native refresh is usually more than enough, especially in movies that come with a 120Hz native rate.
Motion enhancements like Sony’s MotionFlow or Samsung’s Motion Rate can however be useful for smoothing out some more heavily motion blur-laden content sources and for giving sports entertainment a certain smooth, sharp sheen. On the other hand, for movie content, these same technologies, one activated in your TV can also create the famous “soap opera effect”, which makes movie content look bizarrely and somewhat uncomfortably smooth. In other words, go for higher native refresh rates if you can in the 4K TV you buy but understand that further motion enhancement technologies in these TVs only sometimes offer an extra benefit.
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What’s the bottom Line?
The bottom line, in the simplest possible terms is this: For the vast majority of content, a native refresh rate of 120Hz in your 4K TV of choice will be just fine by itself. Some higher quality TVs can even offer excellent motion control with 60Hz native panels and in either case, the differences between 60Hz and 120Hz are minor since no 4K TV content reaches your TV at more than 60Hz anyhow. Real motion enhancement technologies (Those which are double native refresh rate) are a good bonus for activation in specific situations but no motion enhancement rate beyond 240Hz is anything more than an arbitrary piece of marketing fluff, so don’t even pay attention to stated rates like 480Hz, 720Hz or more.
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Most 4K home entertainment content today doesn’t need motion enhancement in a quality 4K TV.
Story by 4k.com
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