Well, unsurprisingly, one of the hot topics for TV set makers and brands at IFA was 8K. The question that was provoked by LG’s booth was “When is 8K not 8K?”. What did they mean?
Of course, the background to this was that LG is starting to talk about shipping an 8K OLED TV set and has to compete with Samsung, which has been trying to get the market hyped up about 8K for a couple of years for the reasons that I explained at the time. (8K is Closer than You Think) Unfortunately, as I have also written before, going to 8K means four times as many transistors between the light source and the viewer. Unless the panel is twice the diagonal (and four times the area), that means a lower aperture ratio and optical efficiency. (Samsung’s Colour Performance Seems to Have Reduced with 8K)
That problem can be solved by boosting the power of the backlight, but then you get other challenges. As I wrote, Samsung already has to work hard to meet the EU Energy ratings. If you can afford a Samsung 8K QLED, you probably don’t worry about the power bill, but those concerned with green issues will care about the high consumption.
However, to achieve the Level D rating, Samsung has had to make its colour filter slightly less aggressive, so the colour is not quite as good as its 4K QLED TVs were last year. At least, that’s the reason that I’m speculating for the drop in performance – but several panel makers that I have spoken to have come to the same conclusion. It has also had to do some other things.
Now, the VA liquid crystal mode that Samsung and most others use for TV panels produces very good contrast when viewed square on, but the contrast performance and degrades quite quickly when you are off-axis and the colours shift. To fix this, VA panel makers divide up sub-pixels into multiple domains – typically at least four – each of which has the molecules slightly differently aligned, by electrical fields or by physical protrusions on the panel. This allows some ‘averaging’ and means more consistent performance. Samsung has done some amazing work to produce very good performance and uses, as I understand it, 8 sub-domains per sub-pixel, divided into two groups of four. Each of those groups has a slightly different gamma response to achieve the optimum overall effect.
Unfortunately, that kind of technique uses more transistors, which is just about acceptable on UltraHD/4K, but at 8K, these extra transistors would kill the energy efficiency, so Samsung has had to go back to four sub-domains, reducing viewing angle performance. To fix this, Samsung has employed a wide viewing angle film and that means good viewing angles, again. Sadly, that viewing angle film smears the pixels into each other, killing the resolution. Probably.
Chi Mei Visual Technology (CMVT) explained its wide viewing angle film for VA at Touch Taiwan. Image:Meko – click for higher resolution
Normally, and according to the current ICDM measurement standard, the way to measure resolution is to display alternate lines of black and white pixels and measure the contrast between them. For text use, the contrast must be at least 50%, while for images it should be 25%. At IFA, LG was pointing out that the latest 8K QLED panels, with wide viewing angle film, don’t do this – reaching around 12% to 18% depending on the size of the panel. LG has taken the question to two independent labs (Intertek and VDE) that have tested the panels and confirmed LG’s view that they don’t meet the ICDM definition of 8K resolution.
LG Electronics Highlighted the 8K Resolution Issue at IFA – Image:Meko
Now, how you define resolution has been a regular topic of controversy on Display Daily as well as in the ICDM and elsewhere. So, I asked our own Chris Chinnock who also is chairman of the 8K Association, supported by Samsung, how they define 8K. He said,
“The Certification work Group in 8K Association will now take up the issue of the test methods to validate each specification in the 8K TV Test Spec. Using contrast modulation is one method for verifying the physical count of the pixels. This and other methods will be considered by the WG in the coming months to agree on a method that best meets our needs.”
Clearly, it might be a bit of an embarrassment for Samsung and the 8K Association if Samsung’s own sets can’t meet the spec. On the other hand, the CTA has also recently published its requirements for ‘8K TVs’ (CTA Launches Industry-Led 8K Ultra HD Display Definition, Logo Program) and has confirmed that to claim 8K resolution, the ICDM standard is mandated. Frankly, that seems to me the way to do it and if the 8K Association doesn’t match that, it’s logo will be substantially devalued.
(A company in the supply chain was also showing 4K & 8K LCDs with a microscope to show how the pixels were blurred, but ‘no photos’ we were told, which was frustrating, to say the least! The same company was also showing how a form of sub-pixel addressing or spatial dithering was also being used which gave some slightly distracting artefacts with some patterns on the screen, but again, ‘no photos’. We also heard that other issues with the Samsung 8K sets, seen by observers at IFA, included ‘strange issues’ in the prism sheet in the backlight and we also heard that Samsung’s 8K scaling can spot the chromatic aberrations from camera lenses and amplify them, as it doesn’t realise that these are not wanted!)
Of course, LG was highlighting that its 8K OLEDs do easily meet the ICDM criteria for resolution – no surprise there. Also of course, the company seems to have forgotten the controversy in the past over its own RGBW LCD panels – or maybe it’s the pain that the company suffered at the time that makes it sensitive on the topic! (BR)
