World Cup Follow-up (Part 2)

After much internet searching and a few cancelled deliveries we finally have our Croatia jersey! A bit too late for the big game but still thought it would be interesting to take a look at the data for both team jerseys:

World Cup Jerseys 3

France vs Croatia jerseys in a 2018 World Cup-themed chromaticity shootout

Like France, Croatia’s jersey happens to fall just inside the BT.709 color gamut. Going back to our original top 10 teams post, it seems like most of the other possible finals matchups would have resulted in a wider color gamut (we did model the Croatian flag red as outside 709).

An interesting follow-up, perhaps for 2022, would be to look at goalie jerseys as well. Goalies wore some of the wildest colors of the competition. France’s Hugo Lorris, for example, wore a super saturated yellow-green for the final match that looked a bit like the tennis ball color we measured recently.

World Cup Follow-up (Part 1)

A few weeks ago I kicked off the World Cup with a survey of the top 10 ranked country’s  colors. At the time, it was impractical to acquire and measure actual jerseys for each World Cup team (32 total) so I limited the survey to top 10 teams and used publicly available data on flag colors under the assumption that jerseys would likely track closely with flags.

Spectroradiomter World Cup Jersey

We’re now down to just two teams so, as promised, I’m back to share some measured data from team jerseys. There is, however, a small issue… Croatia jerseys are sold out everywhere! Probably because it is the first time Croatia has entered the World Cup finals. Luckily, I’ve got one on back-order and will follow-up with yet another update next week, after the big game.

In the meantime, let’s take a quick look at the measured data we do have for France.

France World Cup Jersey Colors

France World Cup 2018 Jersey Colors plotted in CIE 1931

The plot above shows u’v’ coordinates for the three most interesting colors on France’s World Cup jersey: dark blue, light blue and the small pop of red from the back of the collar. As you can see in the plot above these colors actually fall just inside the BT.709 color gamut used for HDTV broadcast. They’re right on the edge though so, if you are watching in HD, you may want to look at having your TV calibrated before the big game for an optimal experience.

The other question that I had after the first post was whether or not the flag data would truly correlate to measured jerseys. In the chart below, I’ve plotted flag data from the original post against new measured data and it seems like my hypothesis held up. At least in the case of France, team colors were reasonably close to flag colors.

France World Cup Jersey vs Flag ColorsLooking forward to providing an update next week on Croatia’s bright red home jersey. In the meantime, may the best team win!

What is the “Color Gamut” of a Fireworks Show?

Editor’s Note: If you read this blog, there’s a decent chance that at some point you’ve gazed up at the impressive spectacle of a July 4th fireworks show and wondered to yourself, “what color gamut, if any, could possibly express all of these deeply saturated, emissive colors??” This week, we’ve got the answers with a timely piece on the chemistry and color of fireworks from guest blogger Allison Harn. Please do not try any of this at home!

Updated 7/6/18 to correct a typo in the chemical compound chart. Hat tip to Matt B. for catching the error!


Fireworks

Image credit: Fireworks via Flickr user ·tic∙ under CC License

If You Are Someone Who Doesn’t Like Fighting After-Show Traffic, Viewing Firework Displays On Tv Is About To Get Better

Ever noticed how disappointing it is to watch fireworks on your home TV compared being out experiencing a live show? If you’re a true fireworks enthusiast, nothing can replace that brilliant burst of color in the sky, followed by a brief moment of anticipation before sound finally catches up to light and the loud THUMP pounds through your chest.

The perfect combination of sound and color are what makes fireworks shows memorable. While I can’t shed light on how sound systems compare to the real deal, I do have insight on why fireworks colors fail you so horribly on current TV’s.

First, A Bit Of Background Chemistry

If you ever took an introductory chemistry course, you might remember performing flame tests on solutions. Electrons get excited by energy from the flames and when they lose that energy, they emit light at specific wavelengths. Each element has its own unique colors that are produced (copper ions emit blue-green; lithium ions emit crimson red). Fireworks compositions work similarly, though it’s a little more complex.

 These grey pellets, called In the pyrotechnics world, the materials that produce colors are collectively called “stars”. The composition of stars varies greatly; it seems like there are more recipes out there for creating a particular color of star as there are for your favorite type of cookie. In the end though, they mostly look the same: black or grey pellets shaped into small cylinders or spheres.

Fireworks and Chemistry 2018 Update
The magic happens when these are ignited. The ingredients combine together at high energies to produce compounds that emit visible light. There are many different color emitters, but the most intense colors come off of the stars that are able to produce Strontium Monochloride (SrCl) for red, Barium Monochloride (BaCl) for green, Copper(I) Chloride (CuCl) for blue, and Calcium Monochloride (CaCl) for orange. These are unstable compounds that are formed in the high temperatures during the chemical reaction.The most remarkable part about this though is that the wavelengths that these compounds emit cannot be displayed by your TV. Current HD TV’s capture only a small part of what the human eye can see. The colors listed above fall almost completely outside the current HD broadcast color space and two of them are beyond even the newer UltraHD TV color space.

Color Fireworks Updated 2018_2.jpeg.001

“Color Gamut” of a fireworks show, plotted in CIE 1976 (u’v’) with comparison to HDTV and BT.2020 color gamuts.

Colors that lie outside the HD TV region in the above chart cannot be accurately displayed by an HD set. These TVs distort what you see by remapping deeply saturated colors so that they fall within the display’s limited color gamut (editor’s note: we detailed how color spaces work in “Color Space Confusion” from 2012). What you see on an HD TV is simply less colorful, less realistic than what you would experience in person.

This is where Quantum Dot TV’s come in. Newer UltraHD TV’s that use this technology can reproduce a much larger range of colors, over 90% of the BT.2020 color space shown above. For fireworks shows, this means that you would be able to experience the true oranges and blues that are part of the displays. Current technology cannot completely capture the red and green colors, but it is much closer than it used to be. These colors will be distorted much less than HDTV’s, providing a significantly improved experience.

When it comes to the 4th, you’ll still find me sitting out in the front row. But if you prefer watching fireworks from the comfort of your own living room, it’s about to get much better. Your pets will probably thank you too.

Reference: http://www.jpyro.com/wp-content/uploads/2012/08/Kos-710-731.pdf

Reposted from the Nanosys Blog, 2016

About The Author

allisonAllison Harn is the Manufacturing Operations Analyst at Nanosys. She has a background in chemistry and before coming to Nanosys taught high school chemistry for several years. Her current position supports operational excellence in quantum dot manufacturing by promoting continual improvement.

2018 World Cup: Watching in 4K HDR makes a difference

Color survey of the Top 10 World Cup countries for 2018

The 2018 World Cup is officially underway with a blowout victory for host country Russia today.

Over the next month, an estimated 3.4 billion (according to GlobalWebIndex) soccer fans will have an opportunity to watch World Cup games in 4K resolution with High Dynamic Range (HDR) and a wider palette of colors. This means the experience of watching the games on TV will be much closer to being at the stadium in person.

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.

To get a sense of how impactful the change from HDTV to 4K HDR might be for World Cup soccer, I did a quick survey of the country colors for the 2018 World Cup’s top 10 teams according to CBS Sports’ most recent ranking.

World Cup 2018 Top 10 Teams Color Gamut

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.

For a full run-down of all the options I recommend Johnny Archer’s thorough review over at Forbes. He breaks it down by country and gets covers the nitty-gritty differences in broadcast features from each of the providers.

Stay Tuned…

I’ll plan to update this with measured data from actual team uniforms once the field has narrowed a bit more in the semi-final or final rounds.

 

 

Introducing Wide Gamut Wednesdays

This week I’m kicking off a new series of posts that set out to answer a simple question:

“Can an HDTV accurately reproduce these colors?”

I’m calling the new weekly feature “Wide Color Gamut Wednesday” or #WideColorWednesday in social media speak. Each week we will analyze a new wide color gamut image and post the results to our @dot_color Twitter feed.

In the process, I think we’ll find that “wide gamut” colors – colors that fall outside the BT.709 color gamut used by HDTVs – are actually fairly common beyond classic examples like Brazilian tree frogs or Coca Cola cans. In fact, in our first test, we found a simple image of spring flowers, taken in Rochester, NY, contained mostly colors that fall outside the BT.709 gamut.

Wide Color Gamut image analysis

62.5% of the colors in this springtime flowers image fall outside the BT.709 color gamut used by HDTVs #WideGamutWednesday

I thought it would be helpful to write up the first #WideColorWednesday image as a blog post with some background on the process used to create these images.

Continue reading

Are tennis balls yellow or green?

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”.

Spectrum of Green and Yellow

According to our Physics textbook, “Fundamentals of Atmospheric Radiation,” the color green is defined as 520-560nm and yellow as 560nm-590nm.

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.

Tennis Ball Color Measurement Nanosys

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:

Tennis Ball Spectra

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).

Tennis ball vs TV Gamut.001

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.

Special thanks to Ernie Lee and Brian Mui!

Watching the World Cup finals this weekend? Your HDTV probably can’t show off Messi’s boots in all their bright blue glory

Lionel Messi laces up some bright blue boots- these super saturated Adidas Sambas were designed for the FIFA World Cup 2014 (image source: Adidas)

Lionel Messi laces up some bright blue boots- these super saturated Adidas Sambas were designed for the FIFA World Cup 2014 (image source: Adidas)

If you’ve been following the FIFA World Cup this summer you may have noticed many players wearing some seriously colorful cleats. These super saturated Sambas are part of a new line-up specially designed by Adidas for the 2014 FIFA World Cup. They are being worn by many of the game’s top players like Argentina’s Lionel Messi who will be wearing his bright blue boots during the finals this weekend.

What you may not know is that, as wild as these shoes appear on your TV, you are actually not getting the whole picture. Today’s HDTV’s are only able to reproduce a limited range of colors- only about a third of what your eye can see- so there’s a lot missing. Common colors from the red of a London bus to Pantone’s color of the year fall outside this small range and watching the games over the past few weeks I’ve been thinking these shoes are also likely to be too colorful for TV.

The horseshoe shaped chart above represents the range of colors that our eyes can see and the triangle contains all the colors an HDTV can show. Lionel Messi's blue cleats fall well outside that range so the color you see on your TV is not accurate.

The horseshoe shaped chart above represents the range of colors that our eyes can see and the triangle contains all the colors an HDTV can show. Lionel Messi’s blue cleats fall well outside that range so the color you see on your TV is not accurate.

So, in honor of this weekend’s World Cup final, I got my hands on a pair of boots that matched my favorite player, Messi’s, and took some measurements to see what I’d find. Turns out that deeply saturated blue falls well outside the range of colors that HDTV’s can produce.

You may not be able to see those blue boots in their full glory unless you are at the stadium but, if the semi-finals are any indication, this weekend’s games should still be pretty exciting to watch!

Is the rec.2020 UHD color broadcast spec really practical?

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

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

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.

Pointer’s Gamut follow-up by TFT Central

figure7_Pointer in CIE1976

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.