Pixels & Diagonals
Last week, a high profile company published an article that incorrectly said that 8K displays had twice the resolution of 4K displays, when, of course, readers of articles on this website will know that they have four times as many. We won’t name the company, but were very happy that they corrected the article immediately when we pointed out the mistake.
However, it got this writer thinking about a topic that he has written about several times over more than two decades, and that is that the display industry could do more to help consumers to understand the benefits of its product features. Why do we use a number that is twice as big to suggest a value that is four times as big? It’s hard to imagine other technology industries that would do the same.
Would a CPU maker boast of a new higher speed chip by giving a number that is the square root of the increase in speed? I doubt it. Would a memory chip supplier quadruple the amount of memory but only give you a number that is twice as big, Again, I doubt it.
How Much Better is 5K than 4K?
Several years ago, the writer was heavily involved in the desktop monitor industry. Monitor suppliers at the time started to produce ‘5K’ displays. Makers were disappointed that sales weren’t as strong as they would have liked.
I was speaking to one supplier about this and I asked “How much better, then is the 5K compared to a 4K?’. He couldn’t give me an instant response – which was surprising for a monitor Product Manager (PM), I thought.
As this happened just before CES that year, I tried an experiment. At CES, I asked all the many PMs that I spoke to from monitor and panel suppliers to answer that question. None gave me an accurate answer and only a couple even made any real attempt. Now, if you think like the person that thought that 8K was double the pixels of 4K, you might think that 5K is 25% better than 4K. However, in terms of pixels, you’d be a long way off.
4K (at least, UltraHD and mainstream 4K) is 3840, giving a vertical number of pixels of 2160. So the ‘4K’ number is effectively ‘rounded up’. On the other hand, 5K is typically 5120 x 2880 (equivalent to four 2560 x 1440 displays). In this case the number is ’rounded down’. So a 4K display has 3840 x 2160 or 8,294,400 pixels. The 5K on the other hand has 14,745,600 or 77% more pixels.
Frankly, it was no surprise to me that marketeers couldn’t get sales for the better product when they didn’t make it clear to potential clients how many more pixels they were getting!
The Camera Industry Gets It
The camera industry, on the other hand, understands that buyers like bigger numbers. If you have a digital camera and are thinking about upgrading, it’s always tempting to go for more megapixels. Sensor makers love to tout their higher numbers. I’m sure that sellers of 5K displays would have done better if they had emphasised that buyers were trading up from 8 megapixels to ‘nearly 15 megapixels’ – that starts to sound like almost double!
There are plenty of smartphones that have sensors with over 200 megapixels1, even though the maximum image that can be created is often much lower (as multiple pixels are combined to reduce noise or the image is cropped). It can be tricky to work out what the handsets can actually produce as an image. In researching this article, we did find this database from a supplier of third party camera software for Android devices. The database lists the maximum resolution image that can be accessed on each smartphone, using their software. And it’s not just about the sensor, lenses are a real challenge as well.
Even extremely expensive professional camera users can struggle to find lenses that can accurately resolve 8K with 33 megapixels, so it would be a surprise if a smartphone could resolve six times more pixels.
What’s a QWUXGA?
We should at least be grateful that the practice of describing all display resolutions in terms of their relationship to IBM PC graphics formats of the 1980s has been declining. although it still persists in some dark parts, particularly in projection. I was always amused by the question “What the XX?!@ is a QWUXGA?” posed by now retired display industry veteran, Mark Fihn 2 It was never clear to me how much someone should pay to have a Q or a W or a U added to the name.
But It’s Not a New Issue
One of the even longer standing mysteries of the display industry is why displays are sold on the diagonal dimension rather than on the area of the image. After all, a 65” TV is more than four times larger than a 32”. Yet the user is presented with a number that is just double. There have been suggestions that
- it was because CRTs (the TV display before flat panel displays) were initially round, so the diagonal made some sense3.
- It was because the diagonal was a bigger number than the width or height and ‘bigger is better’ (but the area number would have been bigger still).
- It was because viewers judged the change in image size from how much larger objects looked in just one dimension – I.e. the figure of a person might be judged as 20% bigger if the image was 20% taller.
It seems most likely that the first reason is the correct one – most industries exist in the context of habit and tradition. (And if you think that display specifications are strange, check out camera sensor sizes!)
In conclusion, more time spent helping consumers to really understand the great benefits of improved specifications could help the display industry to sell more of its higher end products – giving customers a better experience and (usually) helping the industry to get the value it should from its technology developments.
(I should emphasize that these comments are the personal opinion of the editor and do not necessarily reflect the policies of views of the 8K Association!)
- There were 37 listed on GSMArena.com at the time of publication. ↩︎
- A QWUXGA was a Quad Wide Ultra eXtended Graphics Array resolution. That is four times a wide format version of a double enhanced version of IBM’s XGA specification (and introduced in 1990!). XGA was 1024 x 768 and SXGA was 1280 x 1024 making UXGA 1600 X 1200. A wide version of that, or WUXGA, was 1920 x 1200 so a quad version was 3840 x 2400. ↩︎
- The excellent reference book “The Cathode Ray Tube: Technology, History and Applications” by Peter A Keller ISBN 0-9631559-0-3 reports that the big change from round to rectangular CRTs for TVs was in the late 1940s with the change virtually complete by 1950. ↩︎
