4k resolution flat panel televisions, such as the LG 84LM9600 84″ LED LCD, are now 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 previous specification for HDTVs is based on the 1080p standard, which has a resolution of 1920×1080 (2.1 million) pixels. The UHD resolutions are based on multiples of this resolution with the same 16:9 (1.78:1) width-to-height ratio.
4k resolution doubles the number of horizontal and vertical pixels (versus 1080p HD), giving approximately 4 thousand (4k) vertical lines. More specifically, the resolution is 3840×2160 (8.3 million) pixels. In traditional terms, 4k could be called 2160p. This standard is also know as QFHD (Quad Full High Definition, or 4x the resolution of HD 1080p.)
8k resolution gives four times the number of horizontal and vertical pixels vs. 1080p HD, which is approximately 8 thousand (8k) vertical lines. More specifically, the resolution is 7680×4320 (33.2 million) pixels. In traditional terms, 8k could be called 4360p. 8k offers 16 times the resolution of 1080p HD.
The ITU and the Consumer Electronics Association have officially dubbed both 4k and 8k resolution as Ultra High-Definition (but it is sometimes called Ultra HD, or UHD, or UHDTV, or Super Hi-Vision.) This UHD name technically applies to both 4k and 8k, regardless of which of these resolutions it is. However, most manufacturers are clarifying the UHD nomenclature by specifying 4k UHD and 8k UHD.
(Side notes: Digital Cinema 4k has a resolution of 4096 x 2160 due to a slightly wider aspect ratio of 1.90:1. This aspect ratio would not be found in typical consumer products. HDMI 1.4 supports 4k resolutions (both 3840 x 2160 and 4096 x 2160) but is limited to a frame rate of 30 frames per second, so it’s fine for viewing movies filmed at 24 frames per second, but not for 48 frame per second 3D movies or other HFR [60 or 120 frames per second High Frame Rate] material.)
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 enough 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.)
(Note for those of you not used to reading charts: screen size is on the horizontal axis; find your screen size and go straight up until you hit the 4k line. Follow it to the left. That is your minimum seating distance to fully benefit from 4k resolution.)
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
It’s interesting to note that 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.
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]
The Possible Exception: 1080p 3-D Content on Passive (polarized) Screens
Does anyone actually watch 3-D movies at home? No, not really. 3D at home has pretty much flopped. But if you’re one of the few who does, here’s how you may benefit:
There may be a benefit if you who watch 3-D 1080P Blu-ray movies. There are two types of 3-D glasses: more expensive Active Shutter glasses and lower-cost Passive Polarized Lens glasses. Active Shutter glasses deliver the full screen resolution to each eye; Polarized Glasses deliver only half the screen resolution to each eye (540 instead of 1080 vertical lines)
4k allows all 1080 lines to be visible when using Passive Polarized glasses. You wouldn’t be able to get the full benefit from 4k 3-D, but 4k content doesn’t really exist yet anyway.
Obviously, this is only relevant if you 1) own a polarized screen 3-D TV (LG is the most prevalent adopter of this technology) and 2) watch 3-D Blu-ray movies. Based on the abysmal adoption rates of 3-D, I don’t see this being much of a selling point for UHD TVs.
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 to watch. Good luck finding it. Regardless of screen resolution, the source material needs to have the same resolution as the display to see any real advantage. Video Processors will upscale any input to 4k resolution, but upscaling only offers a marginal improvement. Until true 4k and 8k content is widely available, which is a long way off, you are better off saving your cash and getting a 1080p HD TV instead.
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 and low adoption rate, this would seem to have only marginal impact in 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 they stream in real time and that the bit rate is fairly low for a resolution this high. If it’s like their other HD 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.
The benefits of 4k and 8k are marginal at best. You have to sit unrealistically close to see the full detail and you also need 4k source material, which is virtually non-existent. If you want a 3D TV that uses Passive Polarized Glasses, you will gain the ability to view 1080p content at full resolution. If you want to use a PS3 to view 4k photos, you could benefit from 4k. And 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 a 1080p OLED TV instead; the near infinite contrast ratio will offer vastly more benefit than would higher resolution.
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
- Free Burn-your-own Blu-ray: AVS HD 709 – Blu-ray & MP4 Calibration
- Blu-ray: Spears & Munsil High-Def Benchmark Disc (my favorite)
- Blu-ray: Digital Video Essentials: HD Basics (most popular)
- Automatic Calibrator: Datacolor Spyder 3
“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.