Glow in the Dark: Luminance and Bioluminescence

Luminance colors differ significantly from conventional colors for several reasons, including their measurement, uses and applications, visibility, and psychological impact. These differences highlight the unique properties and advantages of luminance colors in various contexts.

Why luminance colors so special

• Studies in marketing have shown that advertisements using high-luminance contrasts (bright colors and clear, bold text) are 70% more likely to attract consumer attention than those with low contrast. This underscores the importance of luminance in visual marketing strategies.
• The Occupational Safety and Health Administration (OSHA) requires that emergency exit signs have a minimum luminance of 5 foot-candles (approximately 54 lux) to ensure visibility during power outages. High-luminance emergency lighting can reduce evacuation times by up to 50%.
• In space, where natural light sources are limited, luminance colors play a crucial role. For instance, the design of spacesuits and spacecraft interiors uses high-luminance colors to enhance visibility and reduce the risk of accidents in low-light conditions.

What are the luminance colors

There isn’t actually a category of colors called “luminance colors.” Luminance itself isn’t a color, but rather a measure of a color’s brightness. This means that all colors have a luminance value, which can be adjusted by altering their saturation and brightness. Here’s a breakdown to clear things up:

• Color is a combination of hue, saturation, and value.
  • Hue is the actual color itself, like red, green, or blue.
  • Saturation is the intensity or purity of a color (Brightness & dullness).
  • Value is the perceived lightness of a color, independent of hue.

https://www.xrite.com/blog/color-attributes-hue-chroma

So, a red color can have high luminance (bright red) or low luminance (dark red). It’s the same hue (red) but with a different level of brightness.

Here’s an analogy: Think of a color like a fruit. The hue is the type of fruit (apple, banana, etc.), saturation is how ripe and intense the color is (bright red vs. dull red), and Value is how light or dark the fruit appears.

Popular colors with high luminance

• White: Universally, white is the color with the highest luminance. It reflects all wavelengths of light and is associated with cleanliness, purity, and light.
• Light Colors: Generally, colors that reflect a lot of light, like light yellows, light blues, and pastels, tend to be popular for their brightness and airy feel. They are often used in homes, hospitals, and design to create a sense of openness and spaciousness.

The Science Behind It

Our eyes perceive luminance through specialized photoreceptor cells called rods and cones. Rods are highly sensitive to light and darkness, allowing us to see in low-light conditions. Cones, on the other hand, come in three types, each sensitive to different wavelengths of light corresponding to red, green, and blue. The combined activity of these cones determines how bright we perceive a color to be. Yellow, for instance, reflects a lot of light across the spectrum, stimulating all cone types and appearing high in luminance. Conversely, blue reflects less light, registering lower on the luminance scale.

Luminance, often the unsung hero of color, is a critical aspect of visual perception. By understanding how it works, we can harness its power to create effective designs, improve accessibility, and appreciate the multifaceted world of color.

Luminance Colors in Nature

Even though our environment contains many dull colors, there are occasions and objects where high-luminance colors are present. Sunlight can also be categorized as a high-luminance light source. Below are some instances where we can see high luminance in our environment:

Earth-Based Luminous Chemical

• Phosphorescent and Fluorescent Materials:
  • Zinc Sulfide: Used in glow-in-the-dark materials, it emits a greenish glow.
  • Strontium Aluminate: Known for its bright and long-lasting luminescence, it emits a blue or green glow.
  • Phosphors: Used in fluorescent lights and TV screens, these chemicals emit light when excited by electrons.

• Bioluminescent Chemicals:
  • Luciferin: Found in fireflies, certain fungi, and marine organisms, this chemical produces light through a reaction with the enzyme luciferase.
  • Chlorophyll: While primarily known for its role in photosynthesis, chlorophyll can emit a red fluorescence when exposed to light.

Cosmic Luminous Chemical

• Nebulae and Star-Forming Regions:
  • Hydrogen (H): The most abundant element in the universe, hydrogen emits visible light in the Balmer series, contributing to the red glow of hydrogen-alpha (Hα) emission lines in nebulae.
  • Oxygen (O): Doubly ionized oxygen (O III) emits a characteristic green light, often seen in planetary nebulae.
  • Sulfur (S): Ionized sulfur (S II) emits light in the red part of the spectrum, contributing to the complex colors of nebulae.
• Interstellar Medium and Supernova Remnants:
  • Calcium (Ca): Supernovae can excite calcium atoms, leading to the emission of light in the visible spectrum.
  • Iron (Fe): Present in supernova remnants, iron emits X-rays and contributes to the overall luminosity of these explosive events.
• Auroras:
  • Oxygen (O): In the Earth’s atmosphere, oxygen can emit green or red light during auroras, caused by the excitation of atoms by solar wind particles.
  • Nitrogen (N): Nitrogen molecules and ions contribute to the blue and purple colors observed in auroras.
• Comets:
  • Cyanogen (CN): The presence of cyanogen in comets can cause a greenish glow in the comet’s coma.
  • Diatomic Carbon (C2): This molecule emits a greenish light, contributing to the greenish hue observed in some comets.

Luminescence in Different Wavelengths

• Ultraviolet (UV) Emission:
  • Carbon (C): Carbon atoms and ions can emit ultraviolet light, which is important in the study of hot, young stars and their surrounding regions.
  • Silicon (Si): Silicon ions emit UV light, often observed in the spectra of hot stars.
• X-Ray Emission:
  • Iron (Fe): Highly ionized iron emits X-rays, contributing to the understanding of high-energy processes in the universe, such as those occurring in active galactic nuclei and X-ray binaries.
• Infrared (IR) Emission:
  • Polycyclic Aromatic Hydrocarbons (PAHs): These complex organic molecules emit infrared light, often observed in star-forming regions and the interstellar medium.
  • Molecular Hydrogen (H2): Emits infrared light, important in cooling processes in star-forming regions.

These luminous chemicals and elements are responsible for the diverse array of colors and light phenomena observed both on Earth and throughout the universe. They play crucial roles in various natural processes, from biological luminescence to the dynamics of stellar and interstellar environments.

Places you can see Bioluminescence

Bioluminescence is a fascinating natural phenomenon where living organisms produce and emit light. As a result, these locations attract many tourists. Here are some notable places and instances where you can observe bioluminescence in nature:

Marine Environments

• Coastal Waters and Bays:
  • Mosquito Bay, Puerto Rico: Known as the brightest bioluminescent bay in the world, this location is famous for its high concentration of bioluminescent dinoflagellates.
  • Luminous Lagoon, Jamaica: Another renowned bioluminescent bay, this lagoon glows due to the presence of dinoflagellates.
  • Laguna Grande, Puerto Rico: Located in Fajardo, this bay also boasts impressive bioluminescent displays.
• Open Ocean:
  • Sailing or Cruising: Phytoplankton and other bioluminescent organisms in the open ocean can create sparkling trails in the water, often visible from boats.
• Marine Life:
  • Deep-Sea Creatures: Many deep-sea fish, jellyfish, and other marine organisms produce bioluminescence to attract prey or mates and to ward off predators. Examples include the anglerfish and the Atolla jellyfish.
  • Coral Reefs: Some corals and reef-associated organisms exhibit bioluminescence, creating enchanting underwater light shows.

Specific Locations

• Toyama Bay, Japan:
  • Firefly Squid: During spring, firefly squid (Watasenia scintillans) gather in Toyama Bay, creating stunning bioluminescent displays in the water.
• Reethi Beach, Maldives:
  • Bioluminescent Plankton: The beaches of the Maldives sometimes glow at night due to bioluminescent plankton, creating a “stars in the ocean” effect.
• Vaadhoo Island, Maldives:
  • Sea of Stars: This island is famous for its bioluminescent plankton that lights up the shorelines, giving the appearance of a sea of stars.

Terrestrial Environments

• Forests and Caves:
  • Fireflies (Lightning Bugs): Found in many parts of the world, fireflies are famous for their bioluminescent mating displays during warm summer evenings.
  • Glowworms: Found in places like the Waitomo Caves in New Zealand and the Glowworm Caves in Australia, these insects create magical glowing displays on cave ceilings.
• Fungi:
  • Bioluminescent Mushrooms: Some fungi, such as those from the genus Mycena and Panellus, produce a greenish glow. These can be found in forests around the world, especially in tropical and subtropical regions. Notable locations include the rainforests of Brazil and the forests of Japan.

Seasonal and Environmental Factors

• Warm, Summer Nights:
  • Fireflies are most commonly seen in warm, humid conditions, typically during summer evenings.
• High Nutrient Waters:
  • Coastal areas with high nutrient levels often experience algal blooms, which can include bioluminescent species of phytoplankton.
• Dark, Undisturbed Environments:
  • Bioluminescence is best observed in dark environments with minimal light pollution, which enhances the visibility of the natural glow.

These locations and conditions provide ample opportunities to witness the enchanting phenomenon of bioluminescence, offering a unique glimpse into the beauty and mystery of the natural world. We will discuss the applications of luminance colors and science behind it with another article which will be released in future.

Author:
Dileepa Fernando
MBA, BSc (Industrial Statistics),
Diploma in Textile Coloration & Finishing, Lean Yellow Belt