The Science of How We See Color—And Why We Need Spectrophotometers
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Have you ever disagreed with a friend, family member or colleague about the color of an object? If so, you’ve experienced how subjective color can be. (Remember the infamous dress that went viral in 2015 because no one could agree on the color?)
There’s a complex science behind color perception, and multiple factors that impact how we see. At the very least, these differences can cause friendly disagreements. However, if accurate, consistent product colors are a critical part of your company’s success, not accounting for these differences can be a costly mistake.
How We See
We see thanks to photoreceptor cells in the retinas of our eyes that transmit signals to our brains. Highly sensitive rods allow us to see at very low light levels – but in shades of gray. To see color, we need brighter light and cone cells within our eyes that respond to roughly three different wavelengths:
Short (S) – blue spectrum (absorption peak ≈ 445 nm)
Medium (M) – green spectrum (absorption peak ≈ 535 nm)
Long (L) – red spectrum (absorption peak ≈ 565 nm)
Perceived color depends on how an object absorbs and reflects wavelengths. Human beings can only see a small portion of the electromagnetic spectrum, from about 400 nm to 700 nm, but it’s enough to allow us to see millions of colors.
This is the basis of trichromatic theory, also called Young-Helmholtz after the researchers who developed it. It was only confirmed in the 1960s, which means this level of detail in understanding wavelengths and colors is only 60 years old.
Meanwhile, opponent process theory postulates that color vision depends on three receptor complexes with opposite actions: light/dark (or white/black), red/green, and blue/yellow.
Together, the two theories help describe the complexity of human color perception.
Color Perception: A Real-World Example
Today, seeing a yellow school bus is a common sight. When “school bus yellow” was voted on in 1939 as the standard color to adopt, we didn’t know as much about color science as we do now.
“The best way to describe [the color] would be in wavelength.”
School bus yellow is actually found in the middle of the wavelengths that trigger our perception of red and green. Because it’s right in the middle, this particular color hits our cones (or photoreceptors) from both sides, equally. That makes it almost impossible for us to miss a school bus—even when it’s in our peripheral vision.
When light hits an object, some of the spectrum is absorbed and some is reflected. Our eyes perceive colors according to the wavelengths of the reflected light.
We also know that the appearance of a color will be different depending on the time of day, lighting in the room, and many other factors. This isn’t such a problem for the average person, but imagine having people evaluating color samples in different offices across the globe. They may perceive different variations of the color based on a range of factors—including their lighting.
Most of us can recognize the color of familiar objects, even as lighting circumstances change (such as a yellow school bus). This adaptation of the eye and brain is known as color constancy. It doesn’t apply to subtle color variations, though, or counteract the changes in color due to the intensity or quality of light.
We might also be able to agree with each other on the wavelengths that define basic colors. However, this might have more to do with our brains than our eyes.
For instance, in a 2005 study at the University of Rochester, individuals tended to perceive colors the same way, even though the number of cones in their retinas varied widely. When volunteers were asked to tune a disk into what they’d describe as “pure yellow” light, everyone selected nearly the same wavelength.
But things get much more complicated when individuals or multiple people try to match colors to a product or material samples. Physical or environmental factors and personal differences between viewers can alter our perception of color. These factors include:
But colors were around for thousands upon thousands of years before there were school buses and stop signs and spectrophotometers. The history of colors and dyes is quite fascinating and dates further back than 2000 BC. There’s no doubt that they had a strong influence even then.
The Mathematics of Color Perception
Since environmental and personal factors influence color perception, we can’t be assured of accurate matches when we’re visually comparing colors to a standard sample. This can cause real business problems like production delays, material waste, and quality control failures.
The CIE color model, or CIE XYZ color space (shown above), was created in 1931. It’s essentially a mapping system that plots colors in a 3D space using red, green, and blue values as the axes.
Many other color spaces have been defined. CIE variants include CIELAB, defined in 1976, where L refers to luminance, A the red/green axis, and B the blue/yellow axis. Yet another model, CIE L*C*h, factors in lightness, chroma, and hue.
Measurement depends on colorimeters or spectrophotometers that provide digital descriptions of colors. For instance, the percentages of each of the three primary colors required to match a color sample are referred to as tristimulus values. Tristimulus colorimeters are used in quality control applications.
The First Step to Overcoming Color Perception Differences
Controlling colors despite unavoidable differences in human perception starts with awareness and education. It’s true that our eyes can only get us so far. Thankfully, there is a range of tools available to ensure the colors of your products are always accurate.
Datacolor offers a complete line of spectrophotometers, software and other solutions suitable for a variety of industries—including plastics, textiles, coatings and retail paint. We also designed an instrument specifically to measure materials that a traditional spectrophotometer cannot measure.
To learn more about color perception, color science and how Datacolor plays a role, dive into one of our blogs below!