What is the "color gamut" of a fireworks show?
Aug 2, 2016
Author: Allison Harn
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!
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 "stars" are the source of the brilliant colors fireworks produce.
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.
Chemical compounds found in fireworks and the wavelengths of light they emit.
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
The HDTV color gamut (rec709) cannot accurately recreate the colors of a July 4th fireworks show. Even BT.2020, the UltraHD color gamut standard, cannot reproduce some reds and greens.
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, nearly 100% 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 HD TV’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
Image credit: Fireworks via Flickr user ·tic∙ under CC License
About the Author
Allison Harn, Manufacturing Operations Analyst at Nanosys
Allison 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.