Does 4K Resolution Matter?

4k resolution televisions are now widely available and potential buyers are wondering if the extra resolution is worth it. In some cases it is, but in most, it’s not.  The details below can help you decide.

What Exactly is 4K (and 8K) Resolution?

The existing 1080- HDTV standard has a resolution of 1920×1080 (2.1 million) pixels. The UHD resolutions are multiples of the 1080p resolution.

4k resolution is named for the approximately 4,000 (4k) vertical lines of resolution it contains. More specifically, the resolution is 3840×2160 (8.3 million) pixels, which is 4 times that of 1080p. (4k is sometimes called 2160p, and is also known as QFHD – Quad Full High Definition.)

8k resolution has about 8,000 vertical lines and 16 times the resolution of 1080p HD. The resolution is 7680×4320 (33.2 million) pixels. 8k is also called 4360p.

The ITU and the Consumer Electronics Association have officially dubbed both 4k and 8k resolutions as “Ultra High-Definition”, but to complicate things, they are also called Ultra HD, UHD, UHDTV, and even Super Hi-Vision.

HDMI 2.0 is required to fully support the 4k specification. However, the existing HDMI 1.4 spec does actually support 4k resolutions, but is limited to a frame rate of 30 frames per second. The problem is that most components with HDMI 1.4 don’t contain the electronics to support the 4k resolution, even if the connection does.

Will I be Able to Notice the Additional Resolution?

To be able to detect the additional resolution of 4k (or 8k), the screen must be quite large and you must sit fairly close. So how do you know if your particular setup would benefit?  Here’s your answer.

Based on the resolving ability of the human eye (with 20/20 vision it is possible to resolve 1/60th of a degree of an arc), it is possible to estimate when 4k resolution will become apparent for the average eyeball. Using the Home Theater Calculator spreadsheet as a base, I created a chart showing, for any given screen size, how close you need to sit to be able to detect some or all of the benefits of a higher resolution screen. (Click the picture below for a larger version.)

Resolution vs. Screen Size vs. Viewing Distance Chart

(Note for those of you not used to reading charts, just jump to the calculator below)

What the chart shows is that, for a 84-inch screen, 4k resolution isn’t fully apparent until you are at least 5.5 feet or closer to the screen. For a “tiny” 55-inch screen, you’ll need to be 3.5 feet or closer. Needless to say, most consumers aren’t going to sit close enough to see any of extra resolution 4k offers, much less 8k.

It’s important to note that research by Bernard Lechner (former VP of RCA Laboratories) found that the average viewing distance of American TV viewers to be 9 feet. This is substantially farther than the 5.5 foot distance required to fully resolve normal-sized 4k screens. I don’t see people rearranging their living rooms to take advantage of the otherwise unnoticeable UHD resolution benefits.

Verification of Calculations by Sony and THX

Sony lists identical required viewing distances in the Frequently Asked Questions section of their product description.  Checkout the Amazon.com product description FAQ for the Sony 65X900A 4k Ultra HDTV. It shows the same distances I have calculated (i.e. 3.6 feet for a 55″ screen and 4.2 feet for a 65″ screen.) If you don’t believe my numbers, confirmation from Sony should help convince you.

Quote from Sony FAQ:
How close to the TV must I sit to appreciate 4K?
The short answer is that between 5 and 6 ft. is the ideal viewing distance for a 55” or 65” Sony 4K Ultra HD TV. However, on a 55“, you can now sit as close as 3.6 ft and enjoy a visibly smoother and more detailed picture (e.g you won’t see the individual pixels). On a 65“ TV, you can sit as close as 4.2 ft. to appreciate 4K.
THX also confirms similar viewing distances:
On a 50-inch 1080p HD display, most consumers can begin to distinguish individual pixels only when standing within six feet of the screen. Therefore if your viewing distance is 10 feet or greater, an Ultra HD 50-inch display will likely have little perceived benefit in terms of image clarity and sharpness [source]

Can you even get 4k and 8k Content?

If you are among the rare few who has a giant screen and sits close enough to it to benefit from 4k resolution, you still need UHD content. Good luck finding it.

As of this writing, the only readily available content source for 4k is the Sony PlayStation 3, and it can only display static pictures (not moving video) using the HDMI 1.4 connection (which only supports a 24 or 30 Hz refresh rate at 4k resolutions.) This may be worthwhile for photographers, but probably not for anyone else. Sony is also offering a UHD movie server that downloads certain Sony Pictures titles in 4k resolution. Due to the limited amount of content, high price, and low adoption rate, this would seem to have only marginal impact on availability of UHD content.

Netflix is offering some material in 4k resolution. I haven’t seen it, so I can’t comment on the quality, but I can say that the bit rate is fairly low for a resolution this high. If 4k is like their 1080p streams, the resolution is OK, but the color banding and color depth are noticeably deficient. Hopefully their 4k streams are of better quality and become more widely available.

In conclusion

The benefits of 4k and 8k are marginal at best. You have to sit unrealistically close to see the full detail and you need 4k source material, which is virtually non-existent. If you use it as a computer monitor to view high resolution source material, you could benefit. Other than that, save your cash and purchase 1080p instead. Or better yet, purchase 1080p OLED TV instead – the near infinite contrast ratio will offer a vastly superior quality image versus 4k resolution on an LED/LCD panel.

ISF states the the most important aspects of picture quality are (in order): 1) contrast ratio, 2) color saturation, 3) color accuracy, 4) resolution. Resolution is 4th on the list, so look at other factors first. Also, be sure to calibrate your display! I recommend the following calibration tools.

Recommended Calibration Tools

“Just tell me what resolution HD TV to get”

If you don’t like reading charts and are looking for a quick answer, enter you screen size below to see how close you’ll need to sit to fully appreciate various screen resolutions.

Enter screen size: inches diagonal

  • For 480p (720×480) resolution, you must sit:
    feet or closer for full benefit
  • For 720p (1280×720) resolution, you must sit:
    feet or closer for full benefit
  • For 1080p (1920×1080) resolution, you must sit:
    feet or closer for full benefit
  • For 4k (3840×2160) resolution, you must sit:
    feet or closer for full benefit
  • For 8k (7680×4320) resolution, you must sit:
    feet or closer for full benefit
Written by in: Home Theater | Tags: , , , , , , , , , , , , , , , , | Last updated on: 2014-May-27 |

111 Comments »

  • Santosh Reddy says:

    Hi carlton, thanx for the chart. Am planning to buy the new 75inch Sony S90, my viewing distance is 9.3 feet away from the tv. Your chart suggested that i sit 10 feet away for watching 1080p content. Does sitting little closer reduce the picture quality ? Please help me… Thank you!

  • Santosh Reddy says:

    Hi carlton, thanx for the chart. Am planning to buy the new 75inch Sony S90, my viewing distance is 9.3 feet away from the tv. Your chart suggested that i sit 10 feet away for watching 1080p content. Does sitting little closer reduce the picture quality ? Please help me… Thank you!

  • :D says:

    “0.59 arc minute PER LINE PAIR. I can find no other research that contradicts this in any way.

    Thus, one needs two pixels per line pair, and that means pixel spacing of 0.3 arc-minute!”

    http://www.clarkvision.com/articles/eye-resolution.html

    Unless I’m mistaken this means that all your calculations are off by about 100 percent.

    • Carlton Bale says:

      As I understand it, 0.6 is what is required to differentiate between 2 line pairs. In other words, the two line pairs look like one line at 0.6 arc minutes, so that is the reference, not 0.3.

    • Michael says:

      The article at clarkvision is correct. In order for a display to be limited by human visual acuity pixel spacing must be 0.3 arc minutes apart. That means if you were to print a grid of black-and-white lines spaced 0.6 arc minutes apart (alternating black and white pixels) you’d just be able to perceive them as distinct lines.

      Apple’s marketing people made this mistake when they first started promoting their retina iPhones. They claimed 300pixels per inch at 1.5feet viewing distance was the “retina limit” because normal human vision can resolve 300 line pairs per inch at that distance. However, in order to actually draw 300 pairs of lines in an inch you need to have at least 600 pixels. High quality photo prints are often done at ~600 pixels per inch for this reason.

      Thing is even getting close (i.e. within a factor of two) to that kind of display resolution is pretty much pointless for video playback where your scenes are going to be limited by things like motion blur, and you’ll practically never be portraying scenes with extremely high contrast.

      IMO there’s a far more appreciable difference in picture quality moving from 24 FPS and 48 FPS film (e.g., the latest Hobbit films) than the difference between native 1080p content and 4k content. At 24fps motion blur limits the resolution of most scenes, not the eye, not your display.

  • reply says:

    Quickly tried your excel calculator, using the calculator to try and get a PPI that is close to the 530 PPI 20×13 inch photo used as an example on that site results in an optimum viewing distance less than half the 20 inches that Clark suggests.

  • In the past, I fully supported Carlton’s calculations. 4K only matters if you sit ridiculously close to a television — too close to enjoy a theater experience. And I wrote about it in my own Blog: http://awildduck.com/?p=2755

    But, this week, I have jumped horse. With 50″ UHD TVs at just $399, all bets are off. Even if you sit close enough only occasionally, I say “Go for it!” My comment about the cost trade off appears below. But separately…

    Separately, I am beginning to suspect that a demonstration of visual acuity is not the supreme test of resolution enjoyment. Let’s say that the average person cannot discern a pattern tighter than 0.3 arc minutes. But acutance perception often goes far beyond visual perception measured by a subtended angle. Acutance is the subjective perception of sharpness that related to the edge contrast. It is the reason that humans peering through a microscope can distinguish when two hairlines cross paths, even if the width of the converging hairs is considerably.

    Similarly, it is the basis of the printed unit bars on a calipers. The user looks at the millimeter lines of two slightly different scales (one is stretched by a few percent). They read the calipers by finding the opposing lines that create one smooth longer line. The technique results in highly precise and consistent readings, yet the lines are too small to provide accurate read without the acutance trick.

    Just as with edge enhancement in a photo (it makes the image “pop”), I am beginning to believe that 4K may provide tangible benefits beyond the classic observation of a tiny arc angle.
    _______________

    OK Readers. It is just over 1 year since I advised against buying a 4K television. I said:

    I will not spend $1 more to get a TV that goes beyond 1080p
    —and—

    Thundering bass, contrast and black level are [more germane to] an immersive and a more exhilarating entertainment experience.
    Retractions in my Blog are uncommon. I cannot recall the last time that I completely reversed my opinion on an issue, even one that simply reflects personal taste in entertainment gear. But this is one such situation. This week, TigerDirect is selling a 50″ UHD (4K) TV with decent specs for just $399. Since this post will live past the current market, let me point out that this is less than ¼ of the market price last year and about ¼ the cost of a smaller 42″ HDTV just 3 or 4 years ago.

    With the advent of cheap and ubiquitous Netflix dongles from Google, Roku and Amazon, I don’t care about so-called Smart TV features. What I do care about is contrast, motion index, sound and black level. If these things are on par with major brands, then we have only one question to face. Can the eye can discern the tight-grain pixels of 4K TV? As we discus above (and as Carlton Bale has explained in detail, very high resolution is only discernible at a close distance…

    …But this ridiculously low cost skews my past arguments. Even if you rarely sit close enough to enjoy the additional 6.8 million pixels, I say “Go for it!” At this price, all bets are off.

  • Michael says:

    If TVs are designed to take advantage of it, there can advantage to having pixels that are significantly smaller than the resolution limit of the eye.
    The line “full benefit of 4k visible” refers to the distance at which you can resolve individual pixels. However, you need at least 120 pixels/degree to be able to display image content with 60 line/degree features. (Nyquist theorem). This is perfectly analogous to how CD’s have sample rates of 44kHz so that they can playback audio content with frequency content up to 20kHz (hearing limit).
    In practice you still see perceptible benefits with even higher pixel beyond the nyquist limit because real world anti-aliasing algorithms are imperfect and can still result in perceptible degradation of edge contrast even at 120pixels/degree.
    With sub-resolution limited pixels, dithering techniques can also be used to improve the effective dynamic range of a display. For 1080p content on a 4k TV. 4 8-bit pixels ganged into a single superpixel could be used to display amplitude with 10-bits/color.

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