Different types of light sources emit the various wavelengths(colors) at different levels of energy. One light may give off a particular wavelength at such a low level of energy that it is barely visible...
...while another emits it so strongly that it is seen as a brilliant color.
Although the color is the same, the intensity of the color experience is very different.
The human eye is most sensitive to light in the middle range of the visible spectrum and sees these colors, the yellow-green range, most easily.
Yellow-green light can be sensed at alower level of energy than other colors.
There is visible light and color beyond the range of human vision.
Some animals and insects cansense colors that are beyond the range of human vision.
For instance, jumping spiders and bees can sense ultraviolet light.
Colors on the edges of human vision can also be sensed with special optical equipment.
For instance,there are specialfilters and lensesthat you canattach to acamera to takephotos usingonly infraredlight.
Sunlight is sensed aswhite, or colorless,but it is actuallymade up of amixture of colors(wavelengths) thatare emitted in acontinuous band.Individual colors canbe seen whensunlight is passedthrough a prism.
The glass of theprism bends, orrefracts, eachwavelength at aslightly differentangle so that eachcolor emerges as aseparate beam.
Under the right atmospheric conditions water dropletswill form natural prisms, and the compoenent colors of sunlight can be seen as a rainbow.
Other light sources, like lightbulbs, emit light perceived as white.
But light sources do not have to emit all of the visible wavelengths for white light to result.
White light is produced as long as a sourceemits the red, green, and blue wavelengths in roughly equal proportions.
Red, green, and blueare the primary colors of light.
Mixing two of the primary colors of light produces a new color.
Cyan, magenta, and yellow are the secondary colors of light.
Wavelengths can becombined in unequalproportions to create additional colors.
Two parts green light and one part redat equal levels of energy provide yellow- green.
Two parts red light and one part green at equal levels of energy provide orange.
All hues, including violets and browns that are notfound as wavelengths in the visible spectrum, can be produced in light by mixing the light primaries in different proportions.
White or colored light seen as a result of a combination of wavelengths is called an additive mixture or additive color.
The lamps in neon signs are one example of a light source emitting a narrow range of wavelengths
General light sources each produce wavelengths in acharacteristic pattern called a spectral distribution curve or spectral reflectance curve.
The spectral distribution curve shows which wavelengths areactually present and the strength of each wavelength relative to the others for that particular type of lamp.
Spectral distribution determines (and describes) the color quality of a light source. Warm Neutral Cool
We think of natural and artificial light as two different entities, but ALL light is visible energy.
Light sources can be • spectral distributiodifferentiated from other • apparent whiteneseach other in two ways:
Daylight is the standard of whiteness for man-made light sources, and because response to sunlight is part of our genetic makeup, it also helps to determine whether lightfrom a given source will be sensed as more or less natural.
About 40% of man-made interior lighting is used for domestic purposes.
The balance is used to illuminate public and commercial spaces.
Incandescent lamps, like the sun, produce light by burning.
The light they emit is a small byproduct of heat - only about 5% of the energy used by an incandescent lamp results in light.
Candlelight, firelight, and incandescent lamplight aresensed as comforting because they emit light in the same way the sun does.
The apparent whiteness of an incandescent lampdepends on the temperature at which it burns, called its color temperature.
Color temperature in lamps is measured in degrees Kelvin (K).
A typical incandescent lamp burns at a relatively low temperature, around 2600 - 3000 K.
Lamps that burn hotter emit bluer light; very white light is hottest of all.
A halogen lamp is a type of incandescent lampwith a gas inside the glass envelope that causes itto burn at a high temperature resulting in a bluer white.
The color temperature of a lamp is used as a measure of whiteness for the color of light produced by the lamp.It does not help to predict how a light source will render the colors of objects.
As a designer, you will need to use mockups in field conditionsto make sure that the lamps you use deliver the right quantity and quality of light for each situation.
Fluorescent lamps produce light in a completely different way.
The interior of the glass bulb is coated with phosphors,substances that emit light when they are bombarded with electrical energy.
The color of a fluorescent lamp depends on the particular makeup of its phosphor coating.
Fluorescent lamps do not burn, so they do nothave an actual color temperature, but they areassigned an “apparent color temperature” to indicate their degree of whiteness.
Fluorescent lights produce separate bands of energy instead of a continuousspectrum, but will still emit all wavelengths at similar levels of energy. Because of our eye’s sensitivity to yellow-green, ordinary fluorescent lamps appear yellow- greenish.
Light that imitates sunlight - continuous spectrum - is sensed as the most comfortable, welcoming and natural.
Some lamps are marketed as “full spectrum,” but that doesn’t really tell you anything about the temperature of the light since it could have various strengths of wavelengths.
Current emphasis on the environment has led to new sources of light like the LED lamp.
LED lamps produce light at low operating cost by combining the output of red, green light-emitting diodes.
LED lamps produce a white, strong light that is excellent for limited uses like car headlamps, but is problematic in interiorenvironments because it contains only the three primary colors and does not have a continuous spectrum.
Lighting level refers to the quantity of available light,regardless of its color makeup.
Lighting level describes the total amount of light coming from the source and is unrelated to its spectral distribution.
A lamp may give off more or less light, but its spectral distribution - thepattern of energy emitted at the different wavelengths - is identical for that lamp no matter what quantity of light it gives off.
Too little available light makes it hard to see colors.
Excessive and uncontrolled light falling on a surface can also impair color perception.
Glare is an extreme, physically fatiguing level ofgeneral light. Glare obliterates color perception and can be temporarily blinding.
Reflectance or luminance is a measure of the amount of light falling on a surface that is reflected back.
It is a measure of the total amount of lightreflected, not the individual wavelengths, or colors.
Reflectance is so important to some products, like interiorand exterior paints, that the percentage of light reflected back from each color, called its LRV (light-reflecting value), is part of the basic information the manufacturer provides.
Lighting level affects our ability to see value, and tomake sense of what we see, but the color of the light does not.
Vision is the sense that detects the environment andobjects in it through the eyes, and is the only way in which color is perceived.
Color vision is experienced in two different ways: either as light directlyfrom a light source, or as light reflected from an object.
In the illuminant mode of vision, colors areexperienced as direct light reaching the eye, like the colors of a monitor screen or a neon sign.
In the object mode of vision, colors are seen indirectly as reflected light.
The tangible things of the real world - objects and theenvironment - are seen in the object mode of vision.
The illuminant mode of vision has two variables: • the characteristics of the light source • and the characteristics of the viewer.
In the illuminant mode of vision, colors are relatively stable.
But every viewer brings their own personal sense andinterpretation to the perception of color.
In the object mode of vision, color is seen as light reflected from a surface.
Color perception in the object mode of vision has three variables:• the characteristics of the light source,• the individual viewer’s visual acuity for color and interpretation of it, and• the light-modifying characteristics of the object.
Light leaving a light source is the incident beam. The reflected beam is light thatleaves a surface and reaches the eye.
The material an object is made ofmodifies light in one of three ways: • Transmission • Absorption • Reflection or scattering
Transmission:the material allows light to pass through, as through glass.
Absorption:the material soaks up light reaching it like a sponge, and the light is lost as visible. It can no longer be seen.
Reflection or scattering:Light reaching the material bounces off it, changing direction
Colorants are special materials that modify light by absorbing some wavelengths and reflecting others.
A colorant can be integrated into the substance of a material, like a color-through plastic...
Here the colorant in bananas absorbs all colors except yellow which is reflected.
In order for an object to be seen as a color, the wavelengths that its colorant reflects must be present in the light surface.
A red dress seen under green light is a black dress.In a parking lot illuminated by the light of yellow sodium lamps,red, green and blue cars are indistinguishable from each other. Only yellow cars can be located by their color.
Colorants don’t absorb andreflect individual wavelengthsperfectly. They may absorbpart of a wavelength andreflect part of it, or reflectmore than one wavelength.So many possibilities existthat the range of visiblecolors is nearly infinite.
Colors seen as theresult of theabsorption of lightare subtractivemixtures.
A Macbeth lamp has a spectral distribution similar to sunlight and is often used under laboratory conditions to measure color.
However, such a lamp has little use for artistssince their products are seen under all types of light, and by all types of people.
Two objects that appear to match under one lightsource but not under another exhibitmetamerism. The objects are called a metameric pair.
Because materials differ in their ability to absorb colorants or accept them ascoatings, it is virtually impossible to color match two very different materials.
It is really only possible to reach anacceptable match, one that is pleasing to the eye.
If your colors are an acceptable matchunder both fluorescent and incandescent lights, they will probably be acceptable under nearly all conditions.
A sample submitted for color matching is a standard.
A match that is perfect under any light conditions is possible only when theoriginal standard and the new product are identical in all ways.
Surface is the outermost layer of a thing, its “skin.”
Different surfaces - rough, smooth, or inbetween - have an impact on the way that colors are perceived.
Value refers to the relative lightness or darkness of a hue.
Only the perception of value is affected by surface texture.
Surface texture has no effect on hue, but a roughsurface will look darker than a smooth surface of the same color.
The smoother the surface, the greater theamount of light that is reflected back directly.
A specular surface is glossy, or mirror-like.
Light leaving a specular surface is reflected soimmediately, and so directionally, that most or all of it is seen as white light.
When a specular surface is viewed from an anglethat is not the same as the angle of the incident beam, some light reaching the underlying colorant can be seen.
The color of a sequined garment is only visible when the sequins are viewed at an angle that allows the color to be visible.
A matte surface is a smooth surface that is very slightly, even microscopically, roughened.
Colors on a matte surface have a flatness andunifsormity under nearly all lighting conditions.
LED lamps are currently offered as both linear and point sources, but LED lamps are an emerging technology and their rendition of color and surface is difficult to evaluate at this time.
The sharper the angle of incident light,the more directional the reflected beam will be.
Raking light describes light from a source that ispositioned at an acute angle relative to a surface.
Specular surfaces appear more glossy, andtextured surfaces dramatically rougher, under raking light.
Varying the textures of a surface allows designers to create a an effect of two or more colors (or moreaccurately, lighter and darker variants of a single hue) using only one material.
A piece of yarn, seen on its long side, is relatively smooth. Cut ends of the same yarn ( a pile, or nap) reflect the identical wavelength but scatter light more widely and appear darker.
A small amount of light is lost each time that light travels from a source to a surface, and when light reaches a surface, a very small amount reflects back immediately.
The sum of this light loss can be so slight that as a practical matter it is unimportant.
The light that remains is reflected, absorbed, transmitted, or a combination of these.
If all of the light reaching an object is either reflected or absorbed, the object is opaque. If all (or nearly all) of the light reaching an object or material is transmitted, that object is transparent.
When some of the light reaching an object or material is transmitted and some is reflected, the object is translucent.
A translucent material can be white or a color,depending on its selective transmission and reflection of various wavelengths
Translucentmaterials may allowa great deal of lightto pass through (andbe very translucent)or transmit verylittle light (and bebarely translucent).
The terms transparent and translucent are notinterchangeable. A truly transparent material is likewindow glass: for all practical purposes, it is invisible.
A translucent material is detectably present, no matter how sheer it may be.
Iridescence is an attribute of surfaces on which the hue changes as the observer’s angle of view changes.
The changes from blue to green that are seen in a butterfly’s wings as it flies...
the flashes of red, purple, and green in the black feathers of a Grackle...
or the brilliant and changing colors of soap bubbles and oil films are iridescence.
Iridescence is anopticalphenomenon thatoccurs withreflected light.
The color is produced by the structure of a surface thatamplifies some wavelengths of light and suppresses others, depending on the angle of the light reaching it.
The amplification of light makes iridescent color extremely vivid – the color that reaches the eyes may be reflected,but in the absence of a modifying colorant it is sensed as pure light.
Because no colorant is involved – nothing that absorbs some wavelengths of light and reflectsothers – it is sometimes called structural color.
Iridescent textiles are brilliantly shimmery, seeming to be one color at one angle of view and a second coloras the fabric moves.
Iridescence intextiles is producedin a variety of ways.There are silk yarns with a molecular structure that creates iridescence as well as synthetic yarns with similar properties.
Most iridescent textiles, however, are made using special yarnsand techniques of weaving. When the warp and weft are made from differently colored and light-reflective yarns, each color appears, vanishes, and reappears as the viewing angle shifts.
There are paints and inks with light-reflecting properties that create convincing iridescent effects on a page. As the observer’s position changes, the color changes.
An impression of iridescence is difficult to create on a screen, because light leaving a screen reaches the eye directly, no matter what the viewer’s position or movements.
Luminosity is a word that appears often in color study. Its real meaning is the attribute of emitting light without heat.
A luminous object is light-reflective, but it does not emit heat.
The word “luminous”is used often todescribe very light-reflecting colors andmedia with a great dealof light reflectance, likewatercolor, dyes, ormarkers.
Indirect light occurs when light from a light sourcereaches a broad, light reflective plane that re-reflects it onto a second surface or object.
In order for this to happen, the light source, the reflective surface, and the target surface or object must be positioned at similar angles to one another.
Moonlight is a familiar form of indirect light. The moon isluminous: it reflects light but does not emit its own energy. Its surface reflects the light of the sun to the earth.
Each time light travels, some of it is lost through scattering.Moonlight is weaker than sunlight because much of the sun’s lighthas been scattered and lost, first on its way from the sun to the moon, then again from the moon to the earth.
Indirect light works inthe same way thatmoonlight does. Lightreaching a white surfaceis redirected to a targetarea. The indirectly litarea appears darker thanit would under directlight, but no change in itsapparent hue takesplace.
Indirect color is aform of indirect light.Indirect color occurswhen general lightreaches a highlyreflective color on abroad plane.
Some of the generallight–and a good dealof the strong color–will reflect onto anysurface that ispositioned to receiveit.
One way to describe the phenomenon of color reflected from one surfact to another is plane reflection.
The design applications most vulnerable to this are architecture andinterior design, where planes of color on walls, floors, and ceilings interact with directional light sources to create potential conditions of light and color reflections.
Filters are materials that transmit (pass through) some wavelengths of light and absorb others.
A red filter placed between a light source and an object allowsonly the red wavelengths to pass through. Other wavelengths are absorbed.
Filters are powerful modifiers of light, so they must be used with realunderstanding of their effects.