8K resolution: Frequently Asked Questions
by Florian Friedrich, November 11th, 2019
After my presentations about 8K in 2019 at various trade shows and events, I received questions from attendees. I’m sharing the most popular questions and answers about 8K here and might update this post from time to time.
What is your personal opinion regarding the 8K resolution of 7.680 x 4320 pixels (33 MP) compared to the 4K resolution of 3860×2160 pixels (8 MP)?
When it comes to comparing 4K against 8K, the biggest benefit I see is the disappearance of any kind of pixel structure. 33 Megapixels at normal viewing distances finally seem to be enough to avoid flickering details and jagged edges without compromising visible resolution. This matters for cameras and displays in the same way.
What do you think about people who claim that there’s no benefit in 8K if you don’t sit extremely close (like less than one picture height away) or if you don’t have sources with at least 8K resolution?
I actually understand where these prejudices come from, but they are not correct. I’m explaining these things in detail in my article 8K resolution: hype or benefit? You don’t need to have an engineers degree in electronics in order to understand that human visual acuity and signal sampling are two different things. We all know that from audio: In order to cover the audible spectrum from 20Hz to 20kHz, we’re using sampling frequencies that are at least twice as high as the highest frequency signal we want to cover. Audio-CD is sampled at 44.1 kHz, audio tracks in movies at least at 48 kHz and Highend-Audio uses up to 192 kHz in order to get rid of aliasing effects. No one would dare to say it’s enough to have 20kHz sampling frequency in audio. This is basic electrical communications engineering, where you can’t ignore the sampling theory. In addition to that, we’re talking about square-shaped pixel structures where geometrical aspects are adding to the challenges. So, we really need proper signal sampling and then it’s easy to see the benefits of 8K even at normal viewing distances. It’s a big benefit to see aliasing artifacts disappear. The resulting pictures are smoother and “more silent” as I like to call it.
At which screen diagonal do you think it makes sense to pick an 8K TV and why?
It always depends on the distance to the TV. But as a rule of thumb: If you’re sitting in up to 4 times distance relative to picture height, and if you have healthy eyes, you may clearly see the benefit of 8K.
Which screen diagonal would you consider ideal for a home theater in 8K and how important is upscaling?
The ideal screen diagonal for immersive home theater should be delivering a similar experience as a center seat in the cinema.
Looking at the relevant standards such as SMPTE EG-18-1994 and THX, the cinema screen is covering about 45 degrees of our field of view (FOV), when we sit in the center of the theater. If you translate that to a 16:9 TV at home, you’ll find that 2.5 times the picture height is an ideal viewing distance. So if you sit about 2.33 to 3 meters (~7.5-10ft ) away from your TV, the ideal pick is a 75-85 inch TV.
Even if you don’t look at 8K contents, good upscaling can make the pixels of lower resolution content disappear and your 8K screen will deliver a smooth experience with less digital artifacts than you might be used to see.
When we had CRT-TVs, TV viewers used a distance of up to about 5 times the picture height, why is that not valid anymore?
Well, CRT-TVs could not be built as big as Flat-TVs because that would have been too heavy and costly and also they had a low resolution. That along with some flickering issues led to recommendations of sitting much further away. It has nothing to do with the limitations of perceived resolution. In fact, you needed a higher distance in order to avoid seeing the shadow mask.
Most TV-Programs are SD or HD, so how many pixels does the TV-viewer really need?
I understand that many people don’t see why they should get an 8K TV when we won’t see a lot of TV-programs in 8K really soon. In fact, we can be happy if linear TV over cable, terrestrial or satellite develops more and more towards Full HD and UHD / 4K. TV production has to happen fast and has to be compatible with existing devices as much as possible. But here is the point: If the TV-viewer at home has a premium display with 8K resolution and proper upscaling, it’s really beneficial for the viewing experience.
So if someone says there’s no reason for an 8K TV just because there’s not enough content, I really can’t follow this argumentation.
Which types of 8K content are most fascinating for you at this time?
I’m producing close-to-8K resolution since 2015 when I started to work with the Sony F65 camera and I was part of several newer 8K projects in postproduction. This is why I love this kind of high-quality 8K motion picture. Most of it plays directly from a USB-Stick on the TV (MP4-Format, HEVC). In addition to that, I’m a passionate photographer and even walk the extra mile to convert some of my RAW-pictures into 8K HDR slideshows. This results in a picture quality that blows away even very experienced picture quality enthusiasts and top-notch photographers. But you don’t need to put that much effort into it in order to see the benefits. For example: If you use your 10 Megapixel smartphone-camera and take a portrait-picture to play it with your 4K-TV, only less than 3 Megapixels remain (because of the black bars and 8MP resolution). On the 8K-TV you, in contrast, you’ll see the full resolution of the image.
There’s a discussion about “Real 8K”, so how important are individual picture quality factors such as Peak Luminance, Contrast, Gamut or Contrast Modulation?
Any display higher display resolution is not relevant if some of the main aspects of display quality are compromised. High Contrast, Wide Color Gamut and a Peak Luminance suitable for good HDR are essential elements for a good and modern display. Compromising these factors means that advantages in resolution become less relevant.
On the other hand, the value for contrast modulation (CM) is not as important as many people might think. 8K is more about getting rid of jagged lines, flickering details and a lot of other artifacts than showing more and more detail. Of course, good 8K sources will show visible improvements on the detail side as well, but what I really appreciate is the smoothness and realistic look of the image. In order to achieve a realistic look, a wide color gamut combined with a good contrast ratio and the ability to reproduce fine details is necessary.
If someone makes you think the contrast in a 1-pixel-grille is what defines resolution, you should not believe it. I’m personally a member of the ICDM spatial subcommittee and as much as we can’t talk in detail about the upcoming next version of the standard, I can tell you there’s a difference between what such measurement tells you and what you can see with your eye. I’d like to state it like that: If you measure CM, you have to look at 2,3,4-pixel-grilles as well. In fact, a high-resolution display that has great values for 2 or 4-pixel grilles might look more pleasing to you while not losing relevant image information in almost all cases of up to 8K content. The key here is the addressability of the pixels and delivering good contrast at relevant spatial resolutions in all directions, including diagonal lines and curves.
When do you expect real 8K contents and do you believe in any UHD Blu-ray Format with 8K resolution?
I hope very fast. Of course, because my company FF Pictures is an experienced service provider when it comes to 8K and we’re always searching for new innovative projects. What I can see is that there is a demand in special areas like digital signage and infotainment. It’s incredible how much detail 8K can bring to the canvas. It seems very likely that 8K will find its way mainly using streaming and satellite rather than physical media. I currently don’t see any indications for an upcoming 8K UHD Blu-ray. What I hope to see is 8K content to be temporarily and securely downloaded, so we can overcome bandwidth limitations.
What kind of TV are you using in your private living room?
You may guess it… I’m currently using a 75” 8K-TV of the 2019 generation of Samsung. Of course, this has to do with the fact that I enjoy checking any 8K contents we created in a living room environment. During the last year, I used linear TV lesser and lesser. My kids are so-called “digital natives”, they have a hard time understanding linear TV or why you can’t touch any screen. It does not seem modern to plan your day around the TV schedule just to see something. I still like some aspects of the linear television concept like seeing old classic movies and documentaries you won’t find on Amazon, Netflix, Apple TV & Co. That’s why I hope more and more TV stations will find their way into streaming the valued content they have.