8K TVs top TV line-ups for a reason
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eeNews Europe
Is there 8K content and does it matter? Is it worth the higher price? These are all valid questions to ask if you are in the market for a new TV. In this article, I’ll talk about some of the common misconceptions around 8K, discuss what is included in these new 8K TVs and conclude with the items to look for if you want to consider buying one.
You Can’t See the Difference – or Can You?
Much of the criticism of 8K TV has been that you can’t see the extra pixel when viewing the TV from typical viewing distances of 8-10 feet. This assessment is based upon standard measure of visual acuity – i.e. how well we can see based on the Snellen eyechart. The argument is that adjacent pixels in an 8K TV are so close that we simply can’t resolve them. While the science behind this conclusion is solid, human vision is far more complex than the simple acuity metric might suggest. The reality is that you can see the difference between a 4K and 8K TV image.
NHK has done research to compare displayed images at various CPDs (cycles per degree or line pairs per degree) to real objects. The goal was to see at what CPD the viewer now thinks the displayed image looks like the real object. Their research suggests that at around 150 CPD, displayed images now look like the real object. This clearly suggests that there is more to vison than simple acuity or the Snellen eye chart test where 20/20 vision corresponds to CPD=30.
If simple visual acuity does not full describe our ability to “see” resolution, what are the mechanisms? There appear to be two other factors at play: Vernier acuity and the brain. Vernier or hyperacuity refers to the ability to discern slight misalignments between lines – an ability that is not possible according to simple acuity descriptions of human vision. Hyperacuity means we can perceive fine details even at fairly long viewing distances.
A classic way to prove this is to show to two line-pairs. One pair has two black lines on a light background with the two lines perfectly parallel. The second pair can be misaligned by just a single pixel and many people can see this – even at some distance away. Because modern displays are pixelated, a line that is not parallel will have stair-stepping. While our normal visual acuity may not see this, our Vernier acuity can. As a result, if 4K and 8K images are displayed on 4K and 8K displays of the same size and viewed at the same distance – all other factors being equal – the 8K image will look sharper or crisper vs. a 4K image even when viewed at 8-10 feet. That’s because the spacing of the pixels on the 8K TV is half that on the 4K TV so there will be reduced stair-stepping – i.e. the 8K display will create a smoother line compared to the 4K display in this example.
It would also appear that the brain does processing on the data sent from the eyes. In the above example, the reduced stair-stepping is reinforced in the brain to create a more analog-like image and hence an increase in the “realness” of the image. Given a high-resolution input to the eyes, the brain does a good job of filling in any missing details (and must work less hard compared to lower resolution inputs). This processing also creates an increased sense of depth.
In other words, simple visual acuity does not tell the whole story on why 8K images look better than 4K even at longer distances. Higher order processes come into play that increase the sense of depth and realness of such images.
Two recent studies are confirming this. In one study by Dr. YungKyong Park of Ewha Womans University in Seoul, side by side 4K and 8K 65” TVs were set up and calibrated at 500 nits of peak luminance. Observers were pre-tested to be sure their simple acuity was 20/20 and that they had normal color vision. All 120 observers sat 9 feet from the displays in a dark room – typical nighttime TV viewing conditions. All participants were shown the same 16 images and 3 videos representing a diverse range of visuals.
As a result of the study, 8K displays performance was rated 35% higher—with perceived image quality increasing by 30% and depth perception increasing 60% from 4K to 8K.
What’s most fascinating is that rather than pointing out the increased sharpness or contrast of the image associated with higher resolution, participants highlighted the main differences to be those related to sensory perceptions – i.e. objects look cooler, warmer, more delicious, heavier.
The researchers concluded that this hyperrealism effect connects the perceptual aspects on the image (contrast, color expression and resolution) with the cognitive aspects perceived by the brain (weight, temperature, reality, space, depth and high image quality). That’s very interesting that the increased resolution has a stronger emotional impact.
A separate study by Dr. Kyoung-Min Lee of Seoul National University looked at the effects of super-resolution (8K) displays from the point of view of the brain. His main conclusions were:
- Super-resolution reduces information loss thus creating a more realistic image
- Super-resolution displays increase the dynamic signal-to-noise ratio reducing cognitive loading and increasing the immersive effect
Having more pixels reduces jaggies in lines and moire effects leading to naturally sharper edges. These sharper edges make it easier to see separate objects allowing for an increased sense of depth. This effect is evident on native 8K content and on upscale/restored content as well.
But more pixels are also very beneficial for creating more realism in colors. Subtle hue changes can result in banding of these colors even if there is sufficient bit depth. Having four pixels to change the hue instead of one leads to a smoother and more lifelike image. This is illustrated in the graphic below. The left shows slight changed in hue while the left side shows the 8-bit RGB values for each color.
The top image represents a 6×6 matrix of pixel that represents the 8K case. A slight change in green hue runs left to right with a slight change in red hue from top to bottom. The bottom case is a 4K display where the average of 4 pixels is represented in this 3×3 matrix of pixels. This shows there can be more banding in a 4K display vs. an 8K display. A smart image restoration algorithm can try to reproduce the more subtle hue changes in the 8K example from a 4K input source. (note: your display may not reproduce these subtle shades which is why the RGB values are shown to prove there is a difference)
The two images below are screen shots from a Samsung 8K TV with and without the image restoration algorithms applied to show the reduction in banding artifacts for subtle hue changes.
Glints or specular reflections also add realism to an image, but these are often tiny parts of the image. Being able to define a high luminance glint in finer detail with an 8K vs. 4K display allows such subtle components to be more accurately reproduced – and increasing realism.
All of these benefits are resolution dependent and apply even if the comparing 4K and 8K high dynamic range (HDR) images. Yes, some of these benefits are subtle, but the brain is remarkable and can processes such subtle improvements to create a more realistic and immersive image with more emotional impact.
What About 8K Content?
It is true that is limited native 8K content today, but that was also true of native 4K content 5 years ago. Today, there is a decent amount of native 4K HDR content available and I believe 8K content will come along at a similar pace in the coming years.
Japan is already broadcast 8K content on an 8K satellite channel and is gearing up to broadcast the full 2020 Summer Olympics from Tokyo in 8K. With this precedent set, it will be hard for major sporting events to now not be captured in 8K. China is expected to be a major market for 8K TVs so content creation is expected to heat up there soon, and also in Korea. In Europe, Rakuten in Spain has announced the first 8K streaming service and SES Astra may be offering 8K satellite service soon as well.
Streaming service providers led the adoption of 4K and I expect them to lead with the adoption of 8K. None have made public announcements yet, but with the introduction of improved compression technologies in the next 2 years allowing 8K streaming at acceptable data rates, don’t be surprised to see these companies vying to be the leader in 8K streaming. And, Sony has announced that the next PlayStation platform, PS-5, will be 8K capable. This is also expected to arrive in 2020.
As you can see, all the pieces are coming together to drive creation of 8K content in 2020 and beyond. But the reality is that almost all content for the next 2 years is going to be in 4K and 2K resolution, so isn’t that a problem? In short, no.
The new 8K TV have very powerful upscaling engines that create an image that has more pixel than the incoming image. Upscaling has been done for decades in all kinds of devices where the incoming image resolution does not match the display resolution. But this term is now obsolete because the algorithms to do this are now much more sophisticated. Maybe a better term is image restoration.
The new techniques use machine learning (ML) and artificial intelligence (AI) algorithms that go well beyond simple algorithms and nearest neighbor scaling concepts. ML techniques use computers to classify types of images and compare low- and high-resolution versions of them to develop tools to allow the computer to then reconstruct a high-fidelity image from a low-fidelity one. AI or “Deep Learning” takes this a step further by adding a feedback loop allowing the system to learn which reconstructions were better than others. The big benefit: the algorithms can get better over time.
Upscaling and image restoration is a very important feature for an 8K TV as it allows images with sharper edges, more texture, reduced jaggies and reduced noise. Many of the providers of 8K TV will implement some form of this image restoration technology, but not all implementations will be equal. Samsung has been showing their image restoration capabilities for some time and they highlight the ability to improve 2K and 4K images to 8K fidelity while also reducing image noise and eliminating compression artifacts.
About the author:
Chris Chinnock is the founder and president of Insight Media – www.insightmedia.info
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