2018 BSJ Blog Fall 2018

Wanna Play with Color Perception?

By Devina Sen

We’ve seen the posts on Instagram, the boomerangs on Snapchat story, and even the special effects in the latest blockbuster films. A person casts multiple colored shadows. A steady camera captures a flickering light revealing a object to be of two drastically different colors or shapes. Light has been an object of fascination throughout time, and on a trip to the San Francisco Exploratorium, I had the wonderful opportunity to explore the science behind these aesthetic phenomena and our perception of color.

Here’s the basics: light is made up of waves that have different wavelengths and frequencies which photoreceptors embedded into our retina transcribe into electrochemical signals. As these signals travel all across the brain, we form a dynamic visual image based on spatial cues, motion receptors, and more.

The crucial fact: objects absorb and reflect light at different wavelengths and the wavelength of the reflected light entering our eyes determines the color we perceive objects to be. The Monochromatic Room at the SF Exploratorium demonstrates this best.

The Monochromatic Room is a small exhibit in which all colors seem to fade into goldenrod. A striped blue shirt looks like a sepia gradient inside the room and a set of crayons that seem like shades of wheat and bronze are revealed to be brilliant hues from pink to green when a flashlight is shone on them. This effect is caused by sodium vapor lamps that emit light waves 589 nm in wavelength, perceived as yellow by the human eye. Since only the lamps illuminate the Monochromatic Room, the objects in the space solely reflect that yellow light back to us, making all the objects seem golden despite the colors they reflect when illuminated by white light from the flashlights. White light is a mix of multiple colors and when shone on different objects and surfaces in the room, such as the crayons, these objects can now reflect light at wavelengths other than 589 nm too — so our eyes perceive the same objects to be different colors than only yellow when light of other wavelengths is present. This exhibit demonstrates how effects such as a “blue wash” in stage performances don’t add lighting that overpowers other colors but instead turn off lights of the undesired colors.

Similarly, the exhibit Colored Shadows takes advantage of the additive nature of white light. Visitors take photos in front of a screen that is illuminated by red, blue, and green light that shine together to create white. When visitors block certain colors of light from hitting the screen, using their bodies or personal items, bright colored shadows appear behind them. The screen still reflects light hitting the blocked area from other directions and causes that area, the shadow, to be colored by whichever lights made up the white color minus the colors of light that are blocked. For example, if I stood straight and blocked a red light from my left and a blue light from my right, the shadow to my right would be made of the colors green and blue (cyan) while the shadow to my left would be red and green (yellow).

A final exhibit challenges our cognitive perception of colors. Named Disagreeing About Color, visitors identify which colored dot from a ring of dots best matches the color of a dot in the center, often different from the choice of other visitors. Visitors then stand back 20 feet and see that their own choice for the best matching dot may change! This happens because the ring of dots are lit by a gradient blend of green and red light while the middle dot is lit by pure yellow light, so visitors’ choices on the best matching dot are based on their red-green perception. By moving back, the viewer’s perception of the colors are altered as the dots appear dimmer and smaller to the viewer. Disagreeing About Color is a reminder that our personal experiences of color are relative both to our objective experiences of the world and to the subjective experiences of others.

It’s different to read about color than it is to challenge your perception in front of your own eyes – literally! But what does this all mean? In terms of digital arts and special effects design, many visual illusions can be created or replicated simply by presenting color in specific conditions (such as the disappearing dots in the Hermann Grid, which you can read about here). Imagine an escape room where flood lights erupt and flash around the participants while the walls are suddenly colored with disorienting, tiled patterns and the participants must rearrange LED bulbs to match the final sequence before time runs out. In day to day life, however, these fun interactions expose the effects of light pollution on our environment, where the light waves emitted from industrialized areas can cause issues ranging from limiting night sky visibility to disrupting ecosystems across the globe. These exhibits also give insight to what life may be like for people with colorblindness or neurological disorders like achromatopsia where people with perfectly functioning eyes and optic pathways do not see color.

Color perception and light is a fascinating area of study with major research implications in a vast array of fields — optometry, film, ecology, civil engineering, and beyond! Taking the time to explore the world past what’s written in our textbooks makes learning an inspiring and thought-provoking experience. So the next chance you get to engage with something new or different, will you choose to dig a little deeper?

 

References:

[Multicolored Hand Effect]. (n.d.). Retrieved from https://ka-perseus-images.s3.amazonaws.com/cefe5bc5faddbacf15333f600e0dd74cfb3d530a.jpg

Brown, R. O., & Strick, J. (2018, October 10). Exhibit: Monochromatic Room | Exploratorium Museum Exhibits. Retrieved from https://www.exploratorium.edu/exhibits/monochromatic-room

Colored Shadows Demo. (2018, August 21). Retrieved from https://www.exploratorium.edu/video/colored-shadows-demo

Hermann Grid. (1997). Retrieved from http://psylux.psych.tu-dresden.de/i1/kaw/diverses Material/www.illusionworks.com/html/hermann_grid.html

The International Dark-Sky Association (IDA). (2017, February 13). Retrieved from https://www.darksky.org/light-pollution/