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My $19.95 art skills ebook
My $19.95 art skills ebook
Much more information on light and color is in my Art Head Start ebook.
Please also see my free sample chapter on lighting 3D models and scenes.
Hue is what people usually mean when they say “color”.
Hue is the frequency of the electromagnetic light wave energy. Frequency is “waves per second”, flowing past the viewer, called “Hertz” and abbreviated “Hz”.
The reciprocal (the inverted viewpoint) of frequency is wavelength. That is, if the distance between wave crests is shorter, then more waves are packed into the same space and so more waves will arrive per second. So, shorter wavelengths mean higher frequencies and longer wavelengths mean lower frequencies.
Red is the lowest visible light frequency and Violet is the highest which people can see. Just below the light we can see is the Infra-red range, which some animals can sense in a vision-like way, and which we can sense as heat. Just above human vision is the Ultraviolet range of frequencies.
Is color purity - not having other Hues mixed in. People think of Saturation as the color's intensity.
The brightness, independent of Hue or Saturation, is the Value. You can see the Value of a color even in a black and white photo. Artists sometimes use the word “Tone” to refer to Value.
The Additive (light mixing) color notation system Primaries are Red, Green and Blue. “Primary” means that any other color can be created by mixing only these three.
Something that people find hard to believe is that equal amounts of red and green light is what we perceive as “yellow”. This may be because many people are used to the “Subtractive” (absorption by pigments) color notation system.
I think the Color Wheel should be called a “Color Compass”, because it's useful to think of the Hues as measured by degrees around a circle.
A Color Wheel is a useful tool, but shows only 1 of the 3 color attributes (Hue). A Color Tree maps each of the 3 color attributes to one of its 3 dimensions, width, depth and height. Hue is displayed around the color tree as a radial dimension, Value is shown as the vertical dimension and Saturation is the horizontal distance from the center.
The color tree was developed by Albert Munsell and is also known as the “Munsell Color Tree”.
Learn more...
Above is an accurate simulation of what actually happens when you shine 3 saturated (pure) light sources of a red, a green and a blue of equal brightness onto a white screen. This is described using the “Additive Color” notation system - as used for photography, television and computer graphics - wherever light sources of different hues are mixed.
When pigments absorb some colors out of the light spectrum and reflect others, we call that ‘'Subtractive Color”’. This 'Subtractive Color' notation system is used where paints, pigments, dyes or printing are involved. Some hues are subtracted from the white light illuminating the object by the pigments of that object (white light is a mix of all hues). Other hues are reflected to your eyes, giving the object its perceived ‘‘color”. Selectively absorbing certain hues is what pigments do for a living.
What happens to the light energy that's not reflected? The pigments convert it to a small amount of heat. In green plants, that energy is also used to make food for the plant (this is called “Photosynthesis”). As a byproduct of photosynthesis, the plants produce the oxygen we humans breathe and they absorb CO2 from the air.
Did you know that you are an “organic microwave receiver”? Yes, light is Electromagnetic Radiation, exactly like radio, television or radar, but way up in the higher microwave frequencies. That is, starting up in the Terahertz (Trillions of waves per second, each shorter than about 100 millionths of a meter or about 39 thousandths of an inch).
Don't let that word radiation scare you. All “radiation” is not the dangerous atomic ionizing radiation. Anything that propagates through space is properly said to be “radiating”. It just means “spreading out”. For example, when you speak to others, you are sending sound radiation out of your mouth. A pebble thrown into a pool of water causes water waves to radiate.
Because much of our education system has become quite poor at teaching science, many people don't realize that all “radiation” is not the harmful type called “ionizing radiation”. Ionizing radiation is electromagnetic radiation of a high enough frequency (and given a long enough exposure time) to have enough energy to modify some atoms - even the atoms you are made of, by “ionizing” them. That is, by knocking free some of their electrons. Some people are even afraid of their microwave ovens, which have absolutely nothing to do with ionizing radiation, but simply vibrate water molecules to heat them up.
Light waves visible to people are not powerful enough to affect most atoms - no matter how long the exposure time. On the other hand, a few very special materials are ultra-sensitive to visible light's feeble energy - such as photographic film, the pigments of the human eye and the light-using parts of plant leaves.
Think about it. Let's say that some high energy electromagnetic energy, like invisible high frequency ultraviolet in sunlight, is hitting you with x number of waves per second (frequency). If an even higher frequency of electromagnetic energy started to hit you, say with 1,000 times as many waves per second, you would be absorbing a lot more energy per second. At some point, either by waiting long enough or by further increasing the frequency, you are going to start getting burned, even though each individual wave has very little energy.
For people, harmful ionizing electromagnetic energy delivery starts with upper frequency Ultraviolet light (given a long enough exposure time) and gets stronger as frequency increases way up into the X-rays, gamma rays, and whatever may be beyond.
Electromagnetic energy, like radio, television, radar or light waves have an electric part and a magnetic part, just as the name suggests. These 2 parts or “fields” travel at right angles to each other.
We can think of a single wave, or a set of different waves, from the point of view of frequency (waves per second) or from the point of view of time (wavelength).
Below we see how this works for a single wave. For a set of waves of different frequencies, we would see a line on the frequency scale for each wave and a wave shape on the time scale for each.
These two different ways to view and think about waves are called “domains” - the “Frequency Domain” and the “Time Domain”.
The Frequency Domain is usually analyzed using an instrument called a “Spectrum Analyzer”.
This is an example of a software Spectrum Analyzer for audio frequencies
(Favorite instrument of Audio/Acoustics/Vibration engineers and other nerds - me too)
From Art Head Start by jim coe
Traditionally, the Time Domain is measured using an electronic Oscilloscope, although many Spectrum Analyzers can also display the Time Domain nowadays.
Wishing you a creative future!
_jim coe
