Cambridge University Research on Vision – Good News or Bad News for 8K?
Some ten years ago (yes, it really was 2015!), an internet meme caused a furore when viewers disagreed on whether a photo of a dress was blue and black or white and gold. It turned out that the dress was actually blue and black but the controversy highlighted that honest viewers can have different opinions even when presented with the same evidence.
A similar situation arose a couple of weeks back after a research report was released in Nature Communications that said that researchers had found that human vision was better in seeing higher resolution than the researchers had originally expected. The researchers also pointed out that the limits that they had found meant no real benefit to 8K for typical TV viewers in the UK. You can find the full article here.
The press reported this initially mainly with headlines suggesting ‘8K has no benefit’, while later and more considered reports said (to quote one) ‘New research challenges the idea that 8K is pointless’ Why such different views?
Having reviewed the articles what is clear is that the different points of view were really based on the kind and size of TV being taken into account.
Size Matters
It’s well understood by vision scientists that to understand the resolution of human vision, you need to get away from fixed viewing distances and image sizes, so researchers tend to talk about the number of ‘cycles per degree’ in an image. That means the number of changes from black to white that can be seen in one degree of the field of view measured at the surface of the eye. This allows the comparison of small images close to the eye or large images further away.
20/20 vision – sometimes understood to be ‘perfect vision’ although it actually represents ‘average vision’ – is around 30 cycles per degree (cpd). Now, the scientists doing this research were interested in the kind of display needed to match resolution so rather than using cpd as a metric, they doubled the number as to display both a black and a white pixel (one cycle), you need two pixels. As two pixels = one cycle, they talked about 60 pixels per degree as being the equivalent of ’20/20 vision’.Â
The researchers confirmed the well known fact that the eye has less resolution in color vision than in black and white and they found that in their tests that the population mean for monochrome viewing was around 94ppd, and they found individuals that could see 120ppd. That ties in with the general view that some with particularly acute vision can see as well as 20/10 vision (which means that the viewer can see at 20 feet viewing distance the same level of detail as most people at 10 feet).1Â
The researchers found when looking at particular colors, the resolution of red/green could be close to that of monochrome at 89ppd.
The Cambridge team developed a calculator that can be used to decide for yourself what resolution is suitable.Â
Good News/Bad News
The question we started with was why did some report these findings as good news and some as bad? It turns out that this is really related to the kind of display size and viewing distance that was thought to be relevant. The UK, where the researchers are based and where the first press reports came from, tends to have relatively small TV sets along with much of Europe and Japan. If you have a small TV, then the researchers are right and the headline result is bad news for 8K. However, if you are in the US or China, then the average TV size is much bigger and 8K is of real value.
The viewing distance is also key to understanding what is needed. When the first HD and 4K sets were introduced, it was often pointed out that viewers did not move the TV set closer to their chairs so the benefit was not as high as it might have been. There is a corollary to this in that, as TV sizes increase, viewers do not move their chairs further back – viewing distances have been quite consistent for a very long time. As consumers get bigger sets they tend to enjoy the higher immersion of the larger screen and then the resolution makes a difference.
So, if you think that viewers want small TVs viewed from a distance, then, arguably, the research results from the Cambridge study was ‘bad news for 8K’. However, all the trends (and we reported on them recently from the 4K HDR Summit) show that viewers are buying bigger and bigger TVs – and in that case the ‘better vision’ that the research identified is ‘good news for 8K’.
(We also noted that the ‘resolution chart’ that is included in the researchers’ calculator for TV size and viewing distance contains ‘5K’ resolution TV options. Although 5K desktop monitors exist, as far as we are aware, there are no 5K TVs in the market at the moment, so the only real alternative is to jump up to 8K).
*Interestingly, although the researchers included a reference to the paper by Masaoka et al that formed the basis of some of the decisions that led to the development of 8K SuperHivision by NHK, Sensation of Realness From High-Resolution Images of Real Objects https://ieeexplore.ieee.org/abstract/document/6407850, the authors make no mention of it, although its conclusion was that ‘the realness of images increased steadily as the image resolution increased up to around 60 cycles per degree, whereafter it gradually approached that of the real objects’. That’s 120ppd and the Japanese researchers found that some could see an increase in ‘realness’ up to 155cpd (>300ppd).Â
- *Interestingly, although the researchers included a reference to the paper by Masaoka et al that formed the basis of some of the decisions that led to the development of 8K SuperHivision by NHK, Sensation of Realness From High-Resolution Images of Real Objects https://ieeexplore.ieee.org/abstract/document/6407850, the authors make no mention of it, although its conclusion was that ‘the realness of images increased steadily as the image resolution increased up to around 60 cycles per degree, whereafter it gradually approached that of the real objects’. That’s 120ppd and the Japanese researchers found that some could see an increase in ‘realness’ up to 155cpd (>300ppd). ↩︎
