Margie's Muse

Metamerism in Action

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Have you ever bought two garments in a store that matched, only to find that when you went out into daylight they didn’t match at all? Or maybe in the bedroom you put on what you thought were two matching socks, but when you got to the kitchen you saw that one was blue and the other was black. The visual discrepancy was probably not because you were tired and bleary eyed. This was metamerism in action.

Have you ever noticed that the colors in your printed photos look great under daylight from a window, but freakish under fluorescent or incandescent lighting? What were clear blue skies are now purple, and your beloved’s beautiful face is now an orange tone uncomfortably reminiscent of Halloween. Even the neutral grays may look goulishly green.

This is metamerism, and its attendant frustration, in action.

Metamerism occurs when you see two colors match under one light source and not match under another.

Metamerism is often an issue when buying carpet, trying to match clothing color, drapes, fabrics, and paint. Colors appear to match in the store but they look completely different in the lighting in your home.

If we didn’t have many different colors of lighting in everyday life, metamerism would not be an issue. It boils down to the difference between how an object affects light, and the color it appears to our eyes.

Lighting affects the way we perceive color. We buy bulbs advertised as “natural” to improve the appearance of people and objects in our home. These bulbs attempt to simulate full spectrum light. Sunlight or daylight is considered full spectrum, meaning that it contains a relatively even distribution of every color in the spectrum from violet through red: all are present at nearly the same intensity. This is the definition of “white”: the presence of all colors at once.

Most artificial lighting, such as fluorescent and incandescent, has an uneven, “spiky” distribution of wavelengths. Each color in the spectrum is not represented equally. Fluorescent lighting has a large green component and is deficient in red, making it (and what it illuminates) look green. Conversely, incandescent lighting has a larger red component and is deficient in green and blue, making it (and what it illuminates) look orange.

If you want to witness this in a controlled experiment, grab a number of identical swatches from the paint department and go to the lighting department of a major home improvement store. They usually have a bank of lights with dividers in between. Place one identical swatch under each light. Study how each light affects the sample.

Lets go back to the sock example mentioned above. The bedroom lighting is incandescent, which contains little light in the blue wavelengths. This makes it harder to distinguish blue colors. The fluorescent light in the kitchen emits more blue light, and thus the dark blue can be more easily distinguished from black. In incandescent light, the socks are a “metameric match.” In fluorescent light, they do not match. The differences in the wavelength distribution between the incandescent and fluorescent lights interact with the differences in the spectral reflectance of the socks to make them appear the same in one light source and different in another.

It is possible to reach an acceptable match that is pleasing to the eye. If a match viewed under both fluorescent and incandescent lamps is acceptable to your eye, most likely it will be acceptable under almost all conditions.

Other than reaching acceptably pleasing matches, there’s nothing you or I can do about metamerism. We have as much control over it as we do the spectral distribution of sunlight. But understanding metamerism makes you feel less crazy when you stare at the god-awful combination you know matched beautifully at the store yesterday.