When hot or flaming objects give off light it’s called incandescence. But some things give off a glow at cool temperatures through a process called luminescence. There are many causes—and many artistic effects—you can create.
In Dinotopia: The World Beneath, (1995), large caverns beneath the island are lit by glowing algae, "sunstone" crystals, and ferns. Although higher plants in our world aren’t known to give off their own light, many things objects are luminescent.
Organisms that can produce light live mostly in the ocean. They include fish, squid, jellyfish, bacteria, and algae. In the deep sea beyond the reach of light, the light patches function to lure prey, confuse predators, or locate a mate.
Land animals that emit light include fireflies, millipedes, and centipedes. Some light-producers are activated by mechanical agitation, creating the milky light in the ocean alongside ships’ wakes. Some kinds of mushrooms that grow on rotting wood emit a dim light called foxfire.
Fluorescence is light that an object converts from one kind of electromagnetic energy of a different wavelenth. Some minerals, such as amber and calcite, will give off colorful visible light when they’re lit by ultraviolet light. Other minerals fluoresce during crystal formation.
Tips and Techniques
1. Set up a dim ambient lighting first, then add the luminescent effects.
2. Luminescent colors often gradate from one color to another along the spectrum.
3. Blue-green colors are most common in the ocean because they travel the farthest through water.
4. Luminescence is very dim and diffuse--it doesn't cast shadows.