Chapter 2 – Excerpt from “The Keys to Color”
The perception of color is a highly personal experience. It can be influenced by one’s emotional state, the quality of your vision, different types of color blindness, life experiences etc. Perception of color however, does follow physical laws and that depends completely on the nature of light.
Color has no physical existence. Only under the presence of light can color even exist. Therefore color is influenced by the type of light, the quality and quantity of light and by the light reflected off adjacent surfaces. Rooms with a lot of natural light will look quite different from morning to dusk and then considerably different at night.
The type of light, ambient and artificial, used to illuminate a room is as important as the color(s) chosen for the architectural surfaces of a room.
Why does a chosen color, that seemed so perfect at the paint store, go “off” when applied to the walls of the target room? Or a color that matches perfectly in the studio change considerably at the worksite? Most often it is because the lights are different from where the selection of color is made, to where the color is installed.
This problem is called metamerism.
Metamerism is a phenomenon that occurs where colors change (color shift) when viewed in different light conditions.
The following swatches are the same color
Here is a list of various artificial and ambient light sources and the way they can affect colors.
|Artificial Light||Ambient Light|
|Incandescent||-||Warm yellow||Early morning/dusk||-||Warm light|
|Halogen lights||-||Slight coolness||Late morning||-||Warm to Neutral|
|Daylight bulbs||-||Cool||Afternoon||-||Coolish tones|
|White fluorescent||-||Very cool||Evening||-||Artificial light|
|Full spectrum lights||-||Neutral to cool|
Fluorescent lights have greatly improved over the years and there are many color temperatures now available. The new CFL (compact fluorescent light) bulbs are growing in popularity and quality and may soon replace incandescent bulbs. These can be bought in a variety of color temperatures.
Metamerism becomes most apparent when the color is chosen in a paint or hardware store, where the illumination is usually cool fluorescent for reasons of economy. These inexpensive cool/white store lights excel at illumination, but are poor in rendering color especially in the warm spectrum (reds, oranges, yellows).
That perfect beige you picked out in the store will shift to “pinkish” on your wall because of metamerism. You did not see the “pinkish” cast of the beige at the paint store because the cool fluorescent lights cancelled that hue. The coolish Northern light coming in through a window makes the beige look perfect during the day but as soon as the warm incandescent lights come on… the pink pops out again.
Metamerism also increases with the number of pigments used to color a product. Because of this, most paint companies limit coloring their paints to a maximum of three pigments. Were you to take two colors that look exactly the same under one light, but one color has six different pigments and the other has three, the colors can change considerably when viewed under a different light.
Be aware of the other colors in a room, as the light reflected off one colored surface will cast itself onto others. We see this most often during the day when the colors in the floor reflect on to the wall surfaces. Red seems to be a predominant color in expensive rugs and the pink cast it reflects will cause no end of problems when one is trying to pick or match a perfect beige or sage color. Natural red oak floors will also cast a pinkish glow to the walls during the day.
These are two ways to measure the type of light and the quality that the light has in rendering color accurately.
Color temperature is a standard way of measuring light color at its source. It is not a measurement of thermal degrees but a measurement along a scale corresponding to a Kelvin rating (K).
Color temperature is the color appearance of the light by a light bulb and the color appearance of the light bulb itself.
A lamp with a low color temperature will have a “warm” appearance (red, orange or yellow).
Conversely, a lamp with a high color temperature will have a “cool” appearance (blue or blue-white).
Think of the warm glow of a candle flame. It is not a very hot flame so the light it casts is warm or reddish in tone.
The filament of a halogen bulb burns much hotter so the light it casts is coolish in tone.
2,000 K: Low pressure sodium lamps
2,600-2,800 K: Tungsten (incandescent) lamps (ordinary household bulb whatever the power)
2,700 K: Warm white lamps
3,200-3,500 K: Halogen and “daylight” lamps
4,000 – 4,600 K: Cool white fluorescents
5,000 – 6,000 K: Average daylight, electronic flash (can vary between manufacturers)
6,420 K: Xenon arc lamp
6,500 – 8,000 K: Full daylight, blue sky
Warm versus Cool Colors
Color wheels are usually divided in half with warm colors on one side and cool colors on the other. Warm colors start with magenta and go to reds, oranges, primary yellow and everything in-between.
Cool colors start with violet and continue with all the blues, greens and up to lime yellow (yellow/green).
Warm versus cool is a matter of perceptionbecause, as you can see on the color temperature chart above (Figure 2.7), cool colors are actually hotter than the so-called warm colors. Think of the blue flame on a stove burner versus a yellow/orange candle flame. In northern climates, the perception comes from memories of the cool blue/grays of winter and the warm bright yellow/oranges of Spring and Summer. Closer to the equator, color is again perceived differently because the angle of the sun is more direct and the warm glow of orange diffuses the harshness of cool colors and softens the brightness of warm colors so that almost any mixture of colors reads as harmonious. The profusion of foliage also helps to complement colors. Think of a flower in the middle of dense leaves. People in the desert states, with sparse, dry wide-open spaces, often prefer beiges and neutrals because they blend into the environment without seeming to jar.
The other part of light quality is color rendering. This is the ability of a lamp to render color accurately and to show color shade variations and contrast more clearly. High color rendition allows us to see objects as we would expect them to appear under natural sunlight.
Color rendition is measured via a complex process on the Color Rendition Index (CRI) scale ranging in value from 0 to 100, with higher values being those closest to natural, indirect sunlight.
You may have noticed in some parking lots at night that it is difficult to tell a blue car from a red car; this is because of the poor CRI of low sodium lamps.
Most old-style fluorescent lamps have a poor color rendering value of 55 – 65 which makes people’s complexions look gray/greenish. A cool white fluorescent may have a color temperature of 4,100K but a CRI of 62. With these lamps, you cannot easily see the difference between deep blue and deep green; reds look more purplish and pinky beiges look taupe.
Newer fluorescent and halogen lamps can have a very good CRI (up to 92) which reveal colors very accurately. The Ott-lite True Color™ line of lamps have a CRI of 90+ and have a very steady light that is restful to the eyes although they are rather low in wattage. Another brighter one is the BlueMax™ 42 watt work station lamp. This is the one that I use when I work with color at night time.
Be wary of some “Full Spectrum” lighting systems. The term is currently used as a marketing device for expensive and ostensively healthy lights that have little scientifically proven value.
In summary, artificial light cannot be judged by a single number, i.e. color temperature. The ability of a light to show color, the CRI, is just as important, especially in color matching.
The amount and direction of sunlight that enters a room will affect colors dramatically. Strong sunlight through a large window will reflect any color on the floor directly on to the walls and ceiling. This ambient light is probably the explanation for when we hear a client remark that they like a color in the morning but not in the afternoon or vice versa. This ambient light will change a white color to an off-white. The light coming through a sheer curtain will also color the room.
You may want to use a compass to determine the orientation of the room before you start color selection. Here are a couple of suggestions:
When the light changes from sunlight to tungsten and mixtures thereof, color will change correspondingly.
The light that comes in through windows will also change according to how high up the room is in a building. A room on the first floor and a room on the twenty-ninth floor will have not only a different quantity of light, but a different quality of light besides. The first floor room will have a lot of light reflected from the ground and surrounding surfaces which will warm it. An upper level room will have unfiltered daylight that will cast a cool tone on surfaces.
In summary, since color is reflected light; the type, quantity, quality and direction of light used to look at a color is all important: that is how the hue will be perceived. You can pick a lamp bulb to harmonize a color scheme or even correct a wayward color. A warm cast can be made cool by switching from a 2,800K bulb to a 4,000K or higher value. A cool cast can be made warmer by switching to incandescent bulbs (for example). The exact rendering of a color can only be achieved using a light source with a high (85+) color rendering index and no reflecting colors. Because of metamerism, a color should be chosen using the same type of light (or close to it) under which it will be used.
The next two chapters will discuss how to adjust colors with pigments to compensate for this “color-shift”.