It’s likely to make a big difference. The World Cup is one of the most colorful sporting events on TV with teams from 32 countries, thousands of flag-waving fans and, of course, wildly colorful cleats.
Color gamut of the 2018 World Cup’s top 10 countries.
With a mix of publicly available data and a little math, I was able to plot the dominant flag colors for the top 10 World Cup countries into the CIE 1931 color space (if you are new to reading color space charts, check out our primer here). Note that I limited the survey to flag colors since data on 2018 uniforms was incomplete and flag colors seem to be featured on most uniforms. I’ve also only plotted the two most dominant or most ‘colorful’ colors, ignoring blacks, whites and grays.
The results were a little bit surprising. Based on this data, just two teams entire flags – Argentina and France – can be accurately displayed on a standard HDTV with the BT.709 color gamut. This means fans with wide color gamut sets will finally be able to see their county’s colors in their full glory when viewing a 4K HDR broadcast.
It’s a great example of the power of HDR and wide color gamut to deliver a lifelike experience that really makes you feel like you are there in the stands in Russia sitting next to a crazy face-painted super-fan waving a flag in support of his country (only without the obstructed view from that flag).
How to watch the World Cup in 4K HDR
If you have a 4K HDR-capable set, the World Cup is available to watch in 4K HDR from a variety of sources around the world this year. Here in the US, TV maker Hisense is making 4K HDR games available for streaming in a partnership with Fox while DirecTV, DISH and Comcast are all offering broadcast options.
Tennis star Roger Federer’s answer to this seemingly innocuous question via twitter user @delaneyanndold caused a bit of a stir on social media earlier this week. According to Mr. Federer, tennis balls are very definitely yellow. He’s certainly an expert when it comes to tennis but how is his color accuracy? We applied some basic science to answer this important question once and for all. The answer might surprise you…
With his world-record 20 grand slam tennis championships, it’s likely few people on earth have spent more time looking at tennis balls than Roger Federer. He’s also backed up by the International Tennis Federation which has required all tennis balls be “yellow” in color for the last 46 years.
Case closed, team yellow for the win right?
Despite this overwhelming evidence in favor of yellow we still weren’t totally convinced. Reminiscent of the 2015 dress color controversy, Federer’s comment had Twitter users questioning reality. It turns out a large chunk of the population are totally shocked that tennis balls might be considered anything but green.
It’s understandable that Twitter users might be so passionate about this issue. After all, it can be a bit mind bending to think that much of the rest of the world sees such a common object as a completely different color.
So which is it? Are tennis balls green or yellow and, more importantly, why would we see them so differently? We had a hunch there might be more to this story so we set out to settle the debate once and for all with science…
Yellow vs Green
Before we answer the question, we need to define the colors yellow and green so we know what we are looking for. There is broad agreement that humans perceive wavelengths of light from 520 to 560 nanometers as “green” and 560 to 590 nanometers as “yellow”.
These two colors are right on top of each other so, right away, it’s easy to see why there might be some confusion here.
Capturing the spectra of a tennis ball with our Photo Research PR 655
With these wavelength ranges in mind for green and yellow, we grabbed our trusty spectroradiometer, our Wilson* Official US Open tennis ball, and captured some data. What we found when we plotted the data surprised us:
Measurement of light reflected from our tennis ball shows that the color is really green and yellow (or chartreuse). Shaded green and yellow regions represent generally accepted wavelength ranges for those colors.
Our original question turns out to be sort of a trick question. Tennis balls are neither green or yellow, they’re actually both green and yellow!
Looking at the data above, our tennis ball has a definite peak of reflected light at 525nm. 525nm is squarely in the green range but we would expect a pure green to have a bit more defined peak. Since we also see a significant amount of energy in the yellow range, a more accurate description of this tennis ball’s color might be “chartreuse” (link: https://en.wikipedia.org/wiki/Chartreuse_(color)) which lies right between green and yellow.
Why do so many people see tennis balls as either green or yellow?
The colors we see are determined by three things: the physical color of light reflected by an object, the physiological, electrochemical process of the eye to convert that light into an electrical impulse and the psychological, the processing the brain does to create an image from that signal. We already measured the physical component so it’s the last piece, the psychological that we’re most interested in in understanding why we might disagree about an object’s color.
Seeing is not passive. Our brains add meaning to the light that our eyes detect based on context and experience and memory. We are continuously and actively re-visualizing and color-correcting the signal that comes out of our retinas.
One of the ways our collective brains may be influenced is by the appearance of tennis balls on TV. If tennis balls appear more yellow or more green on TV, that could shift our perception of the color. To find out if this might be a factor, we plotted our tennis ball into the CIE 1976 color space so we could compare it to a standard TV color gamut (if you’re not familiar with these charts, check out our primer on chromaticity diagrams).
The “color gamut” of a tennis ball, plotted in CIE 1976. Left: tennis ball compared to HDTV BT.709 and UltraHD TV BT.2020 color gamuts; Right: zoomed-in view showing the tennis ball chromaticity is just outside the BT.709 color gamut
Here we see that the tennis ball is a very saturated color that lies right between green and yellow. It’s also interesting that our tennis ball is right on the edge of the BT.709 color gamut used in HDTV broadcast. In fact, if we take a closer look at the zoomed-in chart on the right, the tennis ball is just outside the range of colors used by HDTVs.
Displays cannot simply recreate the exact spectra of light reflected off of a tennis ball that we measured above because displays create color through a totally different process called additive mixing. Displays mix just three primary colors of light (red, green and blue) to recreate millions of colors. In the case of a tennis ball, a display essentially tricks our eyes into seeing chartreuse, by mixing together red and green light. The quality of chartreuse that a display can reproduce is therefore determined by the quality of red and green light a display can reproduce.
Since the tennis ball falls outside the primary colors of the HDTV broadcast signal, this means that the color of a tennis ball is essentially impossible to accurately reproduce on a standard HDTV. Additionally, most HDTVs would not have the correct red and green to recreate our exact shade of chartreuse. As a result, the actual color that most TV viewers experience is based more on the creative decisions of broadcast crews and the color gamut mapping algorithm of their TV, which may be shifting the color more towards yellow.
If that’s the case, it would help explain why so many of us perceive tennis balls as yellow. That’s because they are yellow when they mean the most to us, which is on TV during an important match. This doesn’t quite explain Federer’s perception. Although it is quite possible that he’s watched enough endless hours of film working to improve his game, which he likely cares deeply about, to have shifted his view towards yellow.
It will be interesting to see if our collective tennis ball color perception begins to shift towards green or chartreuse as more and more people adopt UltraHD TVs with wide color gamut capabilities.
*: Note that we chose to use a Wilson ball since it’s the official ball of the US Open and we’re based in the US. As a future experiment, it might be interesting to test the ball used at other events like Wimbledon to see if there’s any international variance in color.
I’ve often advocated on this blog for Pointer’s Gamut as an important design goal for display makers but is it really practical today from a technology perspective? Pointer’s Gamut covers a huge area and it’s odd shape makes it awfully difficult to cover with just three primaries. Rec.2020, the leading Pointer’s-covering color gamut broadcast standard and de facto standard for upcoming UHD broadcasts, demonstrates this perfectly. It uses very deep red and green primaries to ensure that all those purples and cyans can get squeezed it into the triangle.
rec.2020 needs a very deep green to cover 99.9% of Pointer’s Gamut
It’s certainly tough to make a display that can reproduce primary colors that are that saturated and it is especially hard to do so efficienctly. Until now the displays that have come closest rely on an esoteric and power-hungry laser backlight system that can only cover up to about 91% of rec.2020 spec. That is impressive given how ambitious rec.2020 is but a bulky $6,000 laser display doesn’t exactly qualify as practical and it’s certainly not a technology that we are likely to find in a tablet or smartphone anytime soon given it’s low power efficiency.
That may be about to change.
My company, Nanosys, has been working on this problem and we now think it is practical to produce an LED LCD that covers over 97% of rec.2020 using Quantum Dot technology. The latest generation of our Quantum Dots emit light with a very narrow Full Width Half Max (FWHM) spec of below 30 nanometers for both red and green wavelengths. FWHM is pretty obscure spec to be sure but it means that the color is both very pure and accurate. That pin-point accuracy actually enabled us to demonstrate over 91% rec.2020 just by modifying an off-the-shelf, standard LCD TV set with a specially tuned sheet of Quantum Dot Enhancement Film (QDEF).
Nanosys demonstrates over 91% coverage of rec.2020 using Quantum Dots and a standard LCD TV color filter
Very impressive and even a bit better than the performance of that laser TV but still not quite all the way there. What else could be optimized to improve the system and get us closer?
Looking at the spectrum after the color filters revealed a significant amount of blue leaking through the green filter. This leakage was causing the blue point to shift away from the rec.2020 primary. By optimizing the system and selecting a different blue color filter material with a sharper cutoff, Nanosys engineers showed that it is possible to build a display that covers over 97% of the rec.2020 standard– with great power efficiency.
Quantum Dot enhanced displays are in mass production today, they are used in commonly available displays on the market today. Their high power efficiency also means they can be used in all kinds of devices from smartphones to TVs. So, for the first time, it is actually becoming practical to build displays that cover the massive rec.2020 standard and since rec.2020 is part of the UHD broadcast spec this great news for the next generation of 4K and 8K devices.
Last summer I wrote a multi-part series here that looked at how much color gamut displays really need. In those articles I used the gamut of colors found in the natural world, as defined by Pointer, as a possible design goal for an ideal color display. Kid Jansen at TFT Central has followed-up on my piece with a much more detailed look at how several current color gamut standards and devices perform compared to Pointer’s gamut. He’s done some great analysis and it’s well worth reading, check it out here.
In the previous post in this series, I made the case for displays with hybrid, custom color gamuts as a great way to deliver coverage of Pointer’s gamut as well as the most important broadcast standards. We can build the hardware today to support these large color gamuts so its seems like a great solution but there is a catch: nobody is broadcasting or distributing these large color gamuts today. So, are we going to have to wait for broadcasters and content creators to slowly catchup, much like we did with HDTV?
What content delivery looks like today
Content is captured and viewed in a wide variety of gamuts across a range of different devices but only broadcast in one gamut.
Today, content creators are actually shooting in a wide variety of color spaces ranging from RAW to rec.709 to Adobe 1998. They are then forced to cram all of these different sources into the lowest common denominator rec.709 standard for broadcast or distribution. That same content is then displayed on devices with a range of different gamut capabilities from tablets that only cover about 70% of rec.709 to HDTVs that do meet the spec to OLED devices that oversaturate the content.
There’s a lot of diversity on both the capture and display sides and a clear bottleneck in the middle in the form of broadcast and distribution channels.
Adhering to broadcast standards is no longer sufficient to guarantee a good experience for consumers because there’s already too much diversity on the display side alone to rely on one standard. You just can’t be sure that consumers are actually looking at your content on a rec.709-capable device. We’re also losing a lot of the value that creators are capturing and could, in many cases, be delivered to end viewers who have the devices to show it.
How do we get around broadcast standards?
What content delivery looks like tomorrow
The first thing to note is that the internet is democratizing broadcast and distribution channels. With the web we can deliver whatever we want, whenever we want. Some players in the industry, notably Sony, are already doing this with 4K content. If there’s no content available and you believe in 4K resolution, you just deliver your own content directly to your customers.
Wide color gamut displays combined with good color management and the web as a broadcast platform will allow content to accurately be displayed in the original color gamut.
Still, this leaves us with some potential experience problems. If the right display gamut is not matched to the right content the results will be no different and that’s why color management is key. There are several companies working on color management solutions and certification programs for devices that will make it possible for wide color gamut displays to handle a variety of incoming gamuts. Using metadata, for example, a wide color gamut display can be alerted to the presence of Adobe RGB content and then remap that content on the fly to assure that it is displayed accurately on that specific panel.
With great color management, we can maximize the gamut on the display side and pull through the best possible gamut for the device we are looking at. In this way, we can deliver always accurate content that meets the designers intent, wether artistic or commercial.
Google announced an updated version of their Nexus 7 tablet this morning. Central to Google’s pitch was the improved display with both more pixels and more color. The device does feature an impressively high resolution, packing 2.3 million pixels into a 7″ form factor. But, I’m more interested in the color performance and, on this point, Google was vague offering only that the display, “has a 30% wider range of colors.”
What do they mean by that?
It depends on their frame of reference- what color space they are using and what color gamut standard they are comparing against. Since Google talked about the accuracy of HD video at their event, let’s assume that they are referring to the HDTV broadcast standard (rec.709) and using the common CIE 1976 (u’ v’) color space.
When I measured last year’s Nexus 7, I found it could only reproduce about 82%* of the colors found in the rec.709 standard. Color reproduction was not accurate and a little bit undersaturated on this device:
Color gamut of Google’s previous generation Nexus 7 versus the HDTV broadcast standard (rec.709). Plotted in CIE 1976 (u’ v’).
With just a simple calculation, increasing 82% by 30%, you’d get about 106% coverage of the HDTV broadcast standard. While that’s actually a slightly wider color gamut than the standard, it is not uncommon for device makers to use a wider color gamut in order to guarantee the color spec across all devices with some room for manufacturing tolerances. This means video and web content should be displayed accurately and it could make for a great looking display.
We’ll order and measure one as soon as they are available to verify so stay tuned…
* note: I always measure coverage of broadcast standards, not simply total area since that can be misleading. However, in this case, coverage and area are nearly the same since the Nexus 7’s gamut is smaller than rec.709.
Last week I looked at the three “P’s” of human color perception– physical, physiological and psychological– as a way to help define a color gamut for the ideal display. Based on real world examples from art and commerce, I concluded that the range of colors found in nature, as measured by Pointer, provided the best fit with our two design goals which were an accurate and exciting, immersive experience.
This week, I’d like to get a little more practical and take a look at existing color gamut standards to see what we might realistically be able to achieve today.
What fits best?
Color gamut of 4,000 surface colors found in nature as measured by Pointer in 1980 against the color gamut of the iPhone 5.
The first thing you’ll notice about Pointer’s gamut (pictured above again) is that it’s a pretty odd, squiggly shape. This means it is going to be difficult to cover efficiently with a three primary system that mixes just red, green and blue to create all the colors we see, like the LCD found in the iPhone. In order to cover Pointer’s with just those three colors, we’d need to make them extremely saturated. There are proposed standards that take this approach, such as rec.2020, but since they are not practical to implement today from a technology standpoint I’ve decided to ignore them for this discussion.
For the near future, we’ll need to rely on just three colors to get the job done, so what can we do now? Let’s look at two popular wide color gamut standards: Adobe 1998 and DCI-P3:
Current wide color gamut standards Adobe RGB 1998, commonly used by pro photographers and designers, and DCI-P3, used in digital cinema, compared to Pointer’s gamut in CIE 1976
Let’s start with Adobe 1998. Many people are familiar with this color gamut since it is found as an option on many consumer cameras and it is popular among creative professionals. It certainly covers a significantly wider range of colors than the HDTV broadcast standard with a very deep green point. The rich cyans that we talked about in the movie “The Ring” would look great in Adobe 1998. But, we’re not getting any more of those exciting reds and oranges. In fact, Adobe’s red point is identical to the HDTV broadcast standard.
What about DCI-P3 then? Designed to match the color gamut of color film and used in cinemas all over the world, DCI-P3 has a very wide gamut. The reds are particularly deep and, of course, all of the colors from the movies we looked at are covered. Still, it’s missing a lot of the deep greens found in Adobe 1998 and only just fits the green Pantone color of the year. So DCI-P3 is not quite perfect either.
What about a hybrid, custom gamut?
What if we combined the green from Adobe with the red from DCI-P3 and their shared blue point? We’d end up with pretty good, high 90’s percentage coverage of Pointer’s gamut, coverage of all of the existing HDTV broadcast content, full coverage of cinema content from Hollywood and a superior ecommerce experience with most of the colors from the natural world covered.
Hybrid color gamut standard that combines the green point from Adobe 1998 with the deep red of DCI-P3
Looks pretty great and we can make displays now that cover this color gamut with today’s technology. But how would it work on the content side? Would we need to get together and agree on this new standard and then wait for years while it is slowly adopted by content creators and display makers?
Next week we’ll look at how content delivery might evolve to support gamuts like this without the need for major changes to broadcast standards.
Last week I set out to define the ultimate consumer display experience in terms of color performance. I laid out some potential color performance design goals for an ideal display, suggesting that such a display should be both accurate and capable of creating an exciting, immersive experience that jumps off the shelf at retail.
Can we achieve both goals? To find out, let’s start by looking at how we perceive color.
The color of objects that our eyes see in nature is determined by three things: physical, physiological and psychological:
The color of objects that our eyes see in nature is determined by three things: physical, physiological and psychological.
The physical component of our color perception is a constant based on the laws of nature. It is a combination of the quality of the illumination or light source, in this case meaning spectrum it contains, and the reflectance of the object. In the image above, the ball appears red to the eye because it is reflecting red light, while absorbing most the other colors from the light source.
The physiological part of our vision is also a relative constant that is based on the electrochemical processes of the eye. The back of the retina contains photoreceptor nerve cells which transform incoming light into electrical impulses. These electrical impulses are sent to the optic nerve of the eye and onto the brain, which processes and creates the image we see. And that’s where the psychological component comes in.
Let’s look at how each of these components might affect display color performance, starting with the physical, which ought to be something we can measure.
Fortunately, a guy named Pointer has done this for us. For his 1980 publication, Pointer measured over 4,000 samples and was able to define a color gamut of real surface colors, of objects found in nature. The result is commonly called “Pointer’s Gamut:”
Color gamut of over 4,000 colors found in nature as measured by Pointer against the color gamut of the iPhone 5.
This already seems like a great place to start. It immediately looks like a great fit our first ultimate color experience criteria which was accuracy. If we could accurately capture and reproduce all of the colors found in the natural world it would make for a much improved, more accurate ecommerce experience, for example.
But how important are those extra colors? Looking at Pointer’s gamut mapped against the color gamut of the latest iPhone in the chart above, you have to wonder if we really come across these deep cyans and reds in everyday life. Are they just infrequent, rare colors or something worth pursuing for our display?
Turns out we do. As an example, Pantone’s color of the year for 2012 was a deep emerald green that falls outside of both the iPhone’s gamut and the HDTV broadcast standard. This is an important and popular color that appears a bit too yellowish on your computer monitor when you are shopping for the perfect tie on Amazon. So there are some really important colors outside of what the iPhone can display today.
But, what about our second criteria, the lifelike, exciting, immersive experience we want to give consumers? Is the gamut of the natural world enough?
If we look at the second component of the visual system, the physiological component, we’ll see that we can actually perceive a much wider range of colors. The cells in the back of retina can actually detect the entire range of the CIE diagram. That’s almost double the range of colors that Pointer found in nature:
Color gamut of the average human eye vs gamut of colors found in nature as measured by Pointer
This is starting to sound like a much more immersive experience. Maybe we ought to pursue the full color capability of the human eye just like the industry has done for high, “retina” resolutions.
It sounds great but it would be a tall order. It would take quite a lot of power, brightness and extra bit depth to even begin to think about covering a color space this large. There certainly would be a high price to pay in terms of design tradeoffs to get there. So are there any truly valuable colors contained in that extra space, similar to the Pantone color in Pointer’s gamut, that would make us want to go for it?
This is where the psychological component comes into play.
Seeing is not passive. Our brains add meaning to the light that our eyes detect based on context and experience and memory. We are continuously and actively re-visualizing the light that comes out of our retinas.
This may seem hard to believe but this fun demo created by neuroscientist Beau Lotto does a great job of showing just how much our brains actively interpret and change what we see.
The color of the chips has not changed in the video above, just our perception of the color. What’s happening here is our experience is telling us that the color chip in shadow must actually be a much brighter color than the chip under direct illumination, so our brain is just making the correction for us on the fly.
Artists absolutely play on this psychological element of our perception of color, sometimes using totally unrealistic or hyper real colors to make us feel or experience something new or help tell a story. In fact, one of the most influential art instructors of the 20th century, Josef Albers, once said that, “the purpose of art is not to represent nature but instead to re-present it.”
Monet’s The Poppy Field, near Argenteuil
So, whether it’s Monet using saturated and contrasting colors with equal luminance to trick our brains into seeing poppy flowers sway in an imaginary breeze in a 19th century painting or modern films which sometimes rely on the wider gamut capabilities of color film and digital cinema projection to create uniquely cinematic experiences for audiences.
Movies like “The Ring,” for example, which used a deep cyan cast throughout much of the film to create tension and help tell a scary story. Or Michael Bay’s “Transformers” movies, which use deeply saturated oranges, reds and teal greens to create an exciting, eye-popping palette appropriate for a summer blockbuster sci-fi movie about giant robots:
There’s certainly a place for wild, unexpected colors in art. But, as we go through some of these examples, I think we’ll actually find that there is a huge range of expression possible within the gamut of surface colors that Pointer measured. The full range of gamut detectable by the human eye, while exciting to think about, is not really necessary to deliver both accurate and pleasing (engaging) color to our visual system.
So where does that leave us?
In my next post I’ll look at existing wide color gamut standards and content delivery mechanisms to see both what we can do today and what’s next for wide color gamut displays.
In my last post, which focused on the trend towards ever higher resolutions in smartphone displays, I suggested that color performance might be a more useful area of focus for display makers. That’s because, in terms of color gamut, we are a long way from reproducing the full range of colors that our eyes can detect.
For context, let’s add the color gamut of one of the most popular smartphones on the market, Apple’s iPhone, to the chart from my last post:
Best performing smartphones in resolution vs iPhone color gamut performance since 2009.
The latest iPhone only covers about 1/3 of the range of colors our eyes can detect so we’re a long way from matching the acuity of the best displays on the market in terms of resolution. But, how much color do we really need for a great experience?
As a display technologist and color blogger that’s probably the question I’m most frequently asked. If I’m advocating for more colorful displays, how much more am I after? There’s got to be a reasonable limit right?
Perhaps unsurprisingly, the short answer is that it depends on a lot of things. Different applications, from ecommerce to the TV on your living room wall, all require differing amounts of color performance. The environment matters a lot too, if the display will be used outdoors brightness may be a factor. There are slowly evolving broadcast standards and content delivery infrastructure to consider as well. And, of course, technology limitations– what can be achieved today and at what cost?
These are all valid concerns for anyone designing and marketing a new display product but they don’t really answer the bigger question. To me, what we really ought to be asking here is: what would the ultimate consumer experience be in terms of color? To answer that, I think we first need to take a step back, put some the practical stuff aside for the moment, and define what that experience should look and feel like. Once we understand that we can start to put the technological pieces together to achieve it.
What do we want?
So, let’s first ask: what do we want? In a pie in the sky, ideal display, in terms of color performance?
Well, the engineers among us are probably thinking, first and foremost, it has to be accurate and that’s a great place to start. Our displays need to accurately reproduce colors found in nature for increasingly important ecommerce applications, photos we take of our family should look real, not over saturated and professionally created content should be reproduced so that it conveys the artist’s intent without distortion.
But, maybe the marketing folks among us have another criteria in mind and that is a bit more subjective. We want our displays to be immersive and engaging. We want them to jump off the shelf at retail and we want to deliver a unique and exciting experience to our customers.
Can we have both?
To find out, I’ll be taking a look at how we perceive color in my next post.
Screenshot of Adobe’s Kuler app showing color extraction from a photo
Adobe recently released a new iPhone app called Kuler that let’s you extract colors from your surroundings using the phone’s camera. It’s a useful tool that allows designers to capture color inspiration wherever they find it and easily incorporate it into their work via color palettes.
The app also highlights a weakness in current display technology: no display on the market today can actually reproduce all the colors we see in the environment around us. So, even if the camera sensor can capture that color you love, you may not be seeing an accurate representation of it on your device.
The iPhone 5’s LCD display is designed to cover the sRGB/rec.709 color gamut standard used for HDTV broadcasts. And, it looks great but compared to the world we see around us, it’s just not quite as rich. If we plot the iPhone 5’s color gamut against the gamut of colors found in nature, the phone comes up short in important reds, greens and cyans:
Color gamut of the iPhone 5’s display compared to the gamut of colors found in nature. The iPhone 5 comes up short in red, green and cyan.
If DisplayWeek 2013 was any indication, color has once again become a hot topic in the display industry. Color gamuts are getting larger and it may not be long before we see a display that can match what our eye sees in nature. Over the course of the next year, we will start to see more wide color gamut-capable devices as OLED continues to expand marketshare and new technologies like quantum dot LCD begin to enter the market in volume.