Technology
Electromagnetic Spectrum
Light
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Electromagnetic Spectrum
Light
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Light is a form of electromagnetic energy like radio and microwaves. However,
at 300GHz the wave length is 0.1 mm and the em energy starts to behave more like
particles than waves. Light ata 500 THz is in this category.
Light Wavelengths: 400nm to 700nm. Frequency: 500 THz - 900 THz Quantum energies: 1.65 - 3.1 eV The speed of light varies in different mediums. In air, light travels about 186,000 miles per second. In a denser medium, such as glass, light travels about 124,000 Mps.
In 1666, Newton discovered that sunlight passed through a prism reveals the colors of the rainbow. The arrangement of the colors of
the rainbow is called the color spectrum. A very close look at sunlight passed through a prism reveals that the color spectrum is not continuous, but is actually composed of discrete lines of color.
COLOR RELATIONSHIPS
Thomas Young (1773-1829) discovered that by combining just three of the seven colours1; red, indigo and green; the result was white light. From these experiments, these three colours were considered primaries. He also realized that by combining any two of these three, gave you one of the other colours seen in the prism, or secondary colours. Artist Michael Eugene Chevreul (1786-1889) is credited for formulating the first systematic attempt to study and write about the subject of color combining. From his laws of contrast and harmony have stemmed concepts of monochromatic, analogous, complementary and triadic color schemes that are found in most modern art textbooks. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
There are seven hues in the visible spectrum. These seven hues1 are as follows: blue, green, red, cyan, magenta, yellow, and white. You will also see 12 color wheels.
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 An equal-triadic color scheme, developed by Chevreul,
includes three colors on the color wheel spaced equidistantly
apart from one another (at 12:00, 4:00 and 8:00). Examples of
equal-triadic color combinations include: red, yellow and blue;
green, purple and orange; yellow-green, blue-violet and
red-orange; or blue-green, red-violet and yellow-orange.Colours can affect what we think and feel: our moods. The reaction we have to a design -- anger, warmth, power, purity -- can all be bought into an image through the use of colour. Black: The colour of authority and power.
RGB (Red, Green, Blue) HSB (hue, saturation, and brightness) or HSL (hue, saturation, and lightness) It is generally agreed that color can be defined by three qualities: hue, saturation, and brightness (HSB)
See description and examples at OK State.
Lab
Additive Color Mixing
Making colors in this way is based on blending, or adding up colored light, which is why it is called additive color mixing. Combining the three primary colors in specific ratios and known amounts enables us to produce all possible colors. By combining the three primary colors red, green and blue, other colors can be mixed, including white. White light is derived from a ratio of 30% red, 59% green, and 11% blue. This is also the ratio to which a color TV is set for black-and-white broadcasts. Shades of grey can be created by maintaining the ratio percentages and by varying the luminosity to specific values. Subtractive color theory explains how we see objects which do not emit their own light, but rather reflect light that falls incident upon them. In subtractive color theory the primary colors are: Cyan, Magenta, and Yellow. Because these are subtractive colors, when the three are combined, they remove all color and result in black. Subtractive Color Mixing There are several sets of subtractive primaries:
Other Color SystemsThe L*a*b color model is based on the model proposed by the Commission Internationale d'Eclairage (CIE) in 1931 as an international standard for color measurement. In 1976, this model was refined and named CIE L*a*b.L*a*b color is designed to be device independent, creating consistent color regardless of the device (such as a monitor, printer, computer, or scanner) used to create or output the image. L*a*b color consists of a luminance or lightness component (L) and two chromatic components: the a component (from green to red) and the b component (from blue to yellow).
Custom Color Systems
Complimentary Colors When discussing light, (additive theory) complimentary colors are any two colors that combine to create white. e.g green + magenta, red + cyan, blue + yellow. When discussing pigments (paint, ink, etc.), (subtractive theory) complimentary colors are any two colors that combine to create black.
LuminosityBesides differing in color (frequency), light can also differ in luminosity, or brightness. A table lamp emits less light than a halogen lamp, but even a halogen source cannot be compared with bright sunlight, as far as luminosity is concerned. Luminosity depends on the amount of available light. It can be measured and recorded in a numeric value. In the past, it was expressed in Hefner Candlepower, but nowadays Lux is used to express the amount of luminosity. Absolute brightness is not very meaningful, because human eyes don't detect brightness linearly with color. Basically, we see Green as brighter than Blue. So, the term Luminance was invented, which is brightness adjusted to indicate appropriately what we really see. Luminance is Gray tone values computed from RGB via the formula: RGB Luminance value = 0.3 R + 0.59 G + 0.11 B There are other variations of this formula also used, with slightly different numbers. For example, a RGB color of (100, 150, 200) would compute its luminance as
(100 x 0.3) + (150 x 0.59) + (200 x 0.11) = 140
Brightness Values:
Color temperature relates to the fact that when an object is heated, it will emit a color that is directly related to the temperature of that object. The higher the color temperature, the more 'blue' the light, and the lower the color temperature the more 'red' the light. Color temperature of light can be measured in degrees Kelvin (K). Color temperature describes the color quality of a light source in terms of the amounts of red light and blue light. Color temperature is based on what is called a Planckian radiator, or simply a black body. As the temperature of the metal of the black body is raised, it goes from a dull black through red and orange to blue and finally to white heat.Daylight has a color temperature between 6000 and 7000 K. The color temperature of artificial light is much lower: approximately 3000 K. In reality, color temperatures range from 1900 K (candlelight) up to 25,000 K (clear blue sky). Television is set to 6500 K, simulating 'standard daylight'. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|  Around sunrise or sunset, the sun's light must pass sideways through a much thicker layer of the earth's atmosphere, which causes even greater filtering of shorter ("blue" and "green") wavelengths. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Electromagnetic Energy: J - Joule (a measure of energy or work) = A force of one newton acting through 1 meter. Force (Newtons) = mass x acceleration (kg * m/s2) When one is working in the world of physics on an atomic scale, energies are often expressed in eV (electron volts) rather than in joules. 1. Are there only seven colors? - Sir Isaac Newton in his early physics experiments decided the colors of the rainbow were Red, Orange, Yellow, Green, Blue, Indigo and Violet. Many of us remember them as ROY G BIV. Are there only seven colors? Newton believed in numerology and thought special numbers governed all natural phenomena. Seven is a very special number. It took God seven days for the creation, there are seven days in the week, seven openings in our head, seven seas, seven continents and many other important sevens.
See:
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In 1913, Niels Bohr discovered that when you add
energy to the atom, heat it, for example, electrons respond by jumping to a higher orbit. With each jump,
each electron emits a photon of characteristic energy.
Hi
RGB % 50,50,50 75,25,25 100,0,0
Photoshop: Lo 
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RGB % 100,100,100 100,50,50 100,0,0
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RGB % 0,0,0 100,0,0 100,100,100
Photoshop: Brightness - Lo 
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RGB % 0,0,0 50,0,0 100,0,0
In video, the color spectrum contains three primary colors, namely red, green and blue. By combining these three, all the other colors of the spectrum (including white) can be produced.
