8K detail unnoticed by most TV viewers says study

Viewers with better vision more likely to appreciate 8K

by Andy Bassett

A recent study has demonstrated that, under normal TV viewing conditions, most viewers cannot tell the difference between 4K and 8K content.

The double blind study was reported on by Scott Wilkinson for Techhive and involved the sorts of industry heavyweights that give credence to research of this nature. The collaborators included Warner Bros. Pixar, Amazon PrimeVideo, LG and the American Society of Cinematographers (ASC). 

Using a mixture of seven different clips that had been specially prepared for the study, 139 viewers were tested over three days. The final results determined that the majority of consumers showed no preference between 4K and 8K clips, while those with higher visual acuity and at closer viewing distances classed 8K clips as ‘slightly better’ than 4K material.

The degree of detail that each participant could perceive was determined prior to testing using standard acuity scoring which showed that most people who took part in the study had normal 20/20 vision or better, while 39 percent were below the average but with results that were mostly only just below normal. 

The viewing sessions lasted around thirty minutes each during which five participants watched the clips. Two were placed in the front row at a distance of 5 feet from the screen and three on a rear row at 9 feet from the screen.

The content used included the following; two clips from Dunkirk (a close up and a wide shot - both 8K scans from the 70mm film); a clip each from Pixar’s Brave and A Bug’s Life (both rendered in 8K for the study); two clips from Amazon's The Tick show (one in a cave and one on a spaceship - both shot in 8K with a Red digital-cinema camera) and finally some nature footage shot by Stacey Spears of Spears and Munsil fame.

The clips were encoded in HDR10 and the table below gives details of the MaxFALL (Maximum Frame Average Light Level) and Max CLL (Maximum Content Light Level) of each clip.

8K detail unnoticed by most TV viewers says study
Study clips and their HDR10 average and maximum light levels


The 8K clips themselves were downscaled to 4K and then upscaled back to 8K by creating each pixel four times with just a bit of smoothing so the final image is effectively 4K within an 8K 'container'. This was so both 8K and 4K versions looked like 8K to the display to prevent any switching triggers giving on screen clues as to the resolution.

The clips were played on an LG 88Z9 88-inch 8K OLED TV in three individual sequences with the 4K and 8K versions of each clip twice assigned randomly as either A or B and shown in an A-B-A-B pattern. The third sequence was a control using the 4K version of the clip played 4 times with the viewers still seeing an A or B label. Once a single A-B-A-B sequence for a clip had been played, a different clip sequence was shown so that none of a clip’s three sequences were played consecutively. In all, this meant 21 sequences were watched in each 30 minute viewing period.

The participants completed the following assessment for each clip sequence indicating whether A or B was slightly better, better, much better, or the same.

8K detail unnoticed by most TV viewers says study
Study score card used to compare clips A and B


The results were presented in a variety of ways. Firstly, the average of all the responses for each clip showed that 8K clips, on average, were rated ‘marginally better’ than the 4K clips. However, even the highest scoring clip (clip 7 - Stacey Spear’s nature footage) was still closer to ‘no difference’ than ‘slightly better’. Interestingly, splitting out the results for those with 20/20 or better vision saw the perception of some 8K clips as improved over 4K, while others were reduced.

8K detail unnoticed by most TV viewers says study
Average of all results for all participants  (left) and Average of results for participants with 20/20 or better vision (right)  


Going one stage further and looking at just the data for those with the highest visual acuity sitting in the front row saw the most marked results, with the 8K clips of the nature footage (clip 7) and A Bugs’ Life (clip 4) score at the ‘slightly better’ value.

8K detail unnoticed by most TV viewers says study
The average results for participants with 20/10 acuity (better than normal) sitting in the front row (five feet from the screen)


Combining the ‘slightly better,’ ‘better,’ and ‘much better’ responses into a single ‘better’ score removed the nuances in responses so that the test authors could see “the difference between people scoring ‘same’ and ‘better’ on any level.” 

8K detail unnoticed by most TV viewers says study
Results when the three different grades of “better” were combined into a single “better” score


Finally, the breakdown of responses shown as ‘preferred 4K over 8K’, ‘no difference’ and ‘preferred 8K over 4K’ is shown below and the surprise here is the relatively high number of choices that favoured 4K over 8K. 

8K detail unnoticed by most TV viewers says study
Distribution of scores that rated the 4K version better than the 8K version (blue), rated the two versions the same (orange), and rated the 8K version better than the 4K version (green)


Michael Zink, VP of Technology at Warner Bros. and one of the study’s authors commented on this, “I believe the reason you see a large number of people rating ‘4K better than 8K’ is that they really can’t see a difference and are simply guessing.” 

He also noted that for all but one clip most people scored ‘4K the same as 8K’ with only the nature footage receiving more people scoring ‘8K better than 4K’ over the other options.

What to make of it all.

The authors conclude that for the majority of viewers, and under typical viewing conditions, increasing the resolution from 4K to 8K provides no perceptible increase in detail to improve their watching experience.  However, this perceptual difference appears to be partially dependent on the content viewed and here the nature footage draws more favourable responses for the 8K clip over the 4K version "possibly because it has lots of high-frequency detail." Moreover, these perceptual improvements were rated more by those with good visual acuity and at closer viewing distances - in this instance sitting at 5 feet from an 88-inch screen. 

The addition of more screens (of different sizes and perhaps the use of an LCD based 8K screen to compare with OLED) in future studies may offer up further nuances in the data but for the time being it would seems that this study shows 4K offers as much detail as the vast majority of consumers can perceive. 

Quite what the TV industry will do with the results from this small scale but thorough study will be interesting to see. The momentum of 8K is building with most TV manufacturers having 8K models - notable exceptions being Panasonic and Philips - and 8K offers creators more options in terms of post production editing due to the higher resolution, making whatever is captured somewhat future-proof. However for other creators, the expense of a full 8K production might not make sense if most viewers will get no appreciable benefit from the viewing experience.

It’s another can of 8K worms, so why not drop a comment in the discussion thread and let others know what you think of this research.

Source: Techhive.com
Image Source
: Warner Bros.

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