Color often seems like an inherent quality particular to any given object. It’s hard to imagine the sun as anything but a beautiful golden orb. Likewise, it’s hard not to grow wistful when thinking of idyllic summers spent under that sun while staring out into blue ocean waters.
However, you might be surprised to find out that the sun is actually white rather than yellow. Likewise, the oceans are usually as clear as the water we find in streams. These two examples highlight the fact that color, as we experience it, involves reflected light. It also suggests that the colors in the world around us might not be as fixed as we’d assume.
Let’s take a closer look at what metamerism is and how it impacts our ability to see color in the world around us.
Rethinking What We Mean When Discussing Color
Color is only as inherent to an object as its ability to absorb specific frequencies of light. Light that isn’t absorbed by an object will be reflected outward. We think of that reflected light as color. We usually conceptualize vision as a passive process. However, in reality, when we look at a colorful object, we’re taking part in a very dynamic experience.
Light is produced by an outside source, interacts with an object, and is then interpreted by our own eyes and brain. The fact that this is such a complicated process gives rise to events that can seem to be an illusion at first. The colors of the sun and oceans are two examples. But we find an even more astonishing example in something known as metamerism.
What We See Isn’t Always What We Get
Think back to all the mistakes you’ve ever made when shopping for clothing. It’s an experience that most of us find perplexing every now and then. Sometimes clothing looks great on us in the store but lets us down at home. Other times, we pick up something that appears to be a perfect match for the color of an outfit. But when trying it on later at home, the item almost seems to have changed color since we were at the store. It’s easy to write those experiences off as a simple mistake. After all, it’s not like the clothing could have changed colors for no reason.
It’s important to remember again that color isn’t really an inherent property of matter. When we talk about color, we essentially describe the interaction between light, a reflective surface, and our eyes. There are quite a few variables involved in this process. Every specific thing we examine in closer detail within this process has a number of complex subsystems.
For example, our eyes see color through the stimulation of cone cells. We have three different types of cone cells. Each one of these specific categories of photoreceptors works with a different color – red, green, and blue. Again, though, it’s important to keep in mind that this color perception involves the reception of specific wavelengths of light.
Red cones are sensitive to long-wave light. Green cones are sensitive to medium-wave light. And finally, our blue cones are sensitive to short-wave light. It’s also important to remember that all of these wavelengths come from whatever is lighting up an area.
Differences Between Various Sources of Light
When a light source projects the full visible spectrum, it appears to be white. However, our eyes are hardly perfectly tuned instruments for color analysis. We usually get a rough idea of color rather than a mathematically perfect measurement. This can lead to some interesting effects. In the case of metamerism, the problem often stems from differences in seemingly white light.
Two different sources of light might look the same to the human eye. But consider a case where the white light contained less medium-wave light than we’d expect. If it was a slight variation, the light might not seem any different to us than what we’d see under sunlight when outdoors. However, the reflected light from objects can appear a little off due to the differences in light reflection and absorption. In fact, the differences in lighting conditions can make two differently colored objects appear to be a match. This phenomenon is known as metamerism.
So metamerism occurs when two different colors appear to match under one lighting condition but not when the light source changes.
Different Light Can Create the Same Responses
In the previous example of clothes shopping, we can imagine a situation with two different light sources. For example, when we’re in a store, we might look at items under a fluorescent light. Most fluorescent light produces an irregular light emittance curve. This means that an item might appear to be different colors when viewed under fluorescent light and sunlight. Again, this is due to the fact that color is derived from reflection or absorption of light emitted from a specific source. Differences in the source’s light output, even if quite subtle, will result in different visual experiences for people within those conditions.
We can also think of this in terms of raw numbers. The cone cells in our eyes react based on specific wavelengths relating to numbers. We can trigger those specific numbers in a variety of different ways. The most common method is for the full spectrum of light to interact with objects in our line of sight. For example, consider the full spectrum as a variable defined as x. We’ll define a specific object as y. Finally, we can define the value received by our eye as z.
The value of x changes depending on the light source. The value of y is a constant. x-y will always produce the same value so long as the light source isn’t changed. But if we move to a different setting, then x will be redefined. This would send a different end value for z. We’d always have a difference if x changed. But would we actually notice that difference?
If x changed by a minuscule percentile of the whole, then we probably wouldn’t realize there was any difference. This is the case for most lighting changes we see throughout the day. The light output of the sun, LEDs, and fluorescent lighting are all distinct from each other. But the difference is usually so slight that the human eye doesn’t distinguish them much. It’s only in some extreme cases that we see objects appearing to have the same color when, in reality, they’re pretty distinct.
Differences in Individual Eyes
Of course, there’s also some subjectivity involved with color perception. We’ve touched on the fact that human vision isn’t really a perfect tool to measure light or color. Most people have some minor differences in how they perceive color. Age is one of the most significant reasons for these differences. As we grow older, our eyes are subject to both internal and external dangers. As people age, they’ll often incur subtle but still significant issues with their eyes. These issues can impair our cone cell’s reception of incoming light. This might paint the world with a slight tinge of color when compared to a younger individual.
There are a wide variety of other reasons why people might perceive color differently. Color blindness occurs in about 4.5% of the adult population. This will obviously create a very different view of colors when compared to the average. This and other causes of color misidentification between people are categorized as a type of metamerism. Specifically, this phenomenon is defined as observer metamerism.
How Understanding Metamerism Can Improve Our Worldview
In short, metamerism describes the misidentification of two technically distinct colors as being the same. The underlying reason for this misidentification can arise from different causes. It might be environmental due to lighting conditions. Or the metamerism might be due to individual differences in our eyes. But the end effect is the same. We essentially see things quite differently than we’d expect.
This phenomenon is uncommon enough in day-to-day life that we’re typically taken aback by it. But there’s an important lesson to be learned from metamerism. The phenomenon highlights that we’re not just passive observers adrift in a world of color. Every color we see comes to us through a complex interaction between ourselves and the environment. It’s most certainly worth taking a moment every now and then to appreciate just how much goes into seeing the colors around us.