LIGHT & COLOUR

The light and the color ( Pablo)
The light and the rainbow
One of the most attractive phenomenons of the nature is the rainbow. It is when the beams of the light of the Sun across the drops of rain.
The water drops it divides in seven lights of colors. The decomposition of the light in colors is a phenomenon that we know as refraction.
Slide nº1
The colors of the rainbow are seen always in the same order: red - violet, red, orange, yellow, green, blue and blue - violet. These colors constitute the called spectrum of the colors.
Slide nº2
How do we see the colors?
When the light illuminates an object, his surface absorbs everything or part of this light; this property is called absorption.
The part of light that is not absorbed by the surface of an object is rejected and changes his direction, and with it, his sensation of color. This property of the surfaces of rejecting part of the light is called reflection.
The light does not suffer any chromatic alteration when it crosses a transparent surface; this happens, for example, when we look for the crystal of a window. If the surface of the crystal is colored, some colors of the white light remain retained in the surface, and this one stops to spend only the lights that coincide with those of the color of the crystal. In this case, all the colors that we see across him are transformed. When the surfaces are translucent, as the screen of a lamp, the beams of light they multiply his directions blurring the color
To see the color of everything what surrounds us is necessary that it is by day or that the objects are illuminated. All the objects they transmit a sensation of color. It is because to the capacity that his surfaces have, on the one side of absorbing everything, or divides of the white light that illuminates them and for other one, of reflecting the light of color that we see.

Mixture of colors
Synthesis additive: primary colors
Slide nº3
Lights of colors
The lights of colors can be obtained separating into its elements the white light (making it happen for a prism or water drop) or to use filters of colors (putting a transparent screen of color in a lantern).
If instead of illuminating the objects with white light, we do it with lights of colors, these change his aspect because the lights of colors are mixed by the colors of the objects.
If the white light can decompose in the colors of the rainbow, the white light is obtained mixing all the lights of colors, but it is not necessary to use all light of rainbow to obtain it, since we will see later.

• Lights primary
They exist three primary lights, with all the lights of colors are obtained. They are the originals and cannot be obtaining from mixtures. These lights are: blue, red and green.
The white light also can be obtained mixing three primary lights: red + blue + green = white color.

• Lights secondary
They are known as secondary lights the lights that are obtaining when two primary lights are mixed: blue light + green light = cyan light; blue light + red light = light magenta; and red light + green light = yellow light.
The primary lights and the secondary constitute the lights of colors basic.

Synthesis subtractive: primary colors
Slide nº4
Pigments of colors
All the paintings that we know are composed by powders of colors mixed with a cementing agent. The cementing agent is a substance that joins the particles of color, turning this way the powders of colors into matters colorings. According to the class of cementing agent that is used we obtain different types of paintings: water-colors, waxes, pencils and felt-tip pens of colors, pastry, etc.
These powders of colors are named also pigments. The pigments have the characteristic of absorbing and reflecting part of the white light.
The black color is obtained on having mixed many different pigments, but it is not necessary to use all the colors to obtain it.
It is enough to mix three primary pigments
• Primary Pigments
As in the lights of colors, three primary pigments exist and they are: the cyan, the yellow and the magenta. They call this way because they cannot be obtained by mixtures, and because from them there are obtained all the colors that we know.
The primary and secondary pigments are known as basic pigments.
• Secondary Pigments
When we mix two primary pigments we obtain a secondary pigment. The cyan pigment + yellow pigment = green pigment, cyan pigment + pigment magenta = blue pigment and the pigment magenta + yellow pigment = red pigment.

The qualities of the color
The most correct way of defining a color is to describe it depending on his qualities. The qualities of the color are the tone, the value and the saturation. These terms indicate us the possibilities and variations that a color can have.
The tone
Slide nº5
The tone is the name with the one that is named every color, and is described by the colors that compose his mixture. When a tone is yellow and green simultaneously, we must define it as a yellow greenish or green yellowish tone, as approach more the yellow one or the green one respectively. To the tone it is possible to be call him also dye.
The value
Slide nº6
The value is the quality that is in use for describing the degree of brightness or darkness that has a tone, that is to say, the quantity of white color or of black color that has a tone in his composition. Tone magenta can be a very clear magenta, if in addition it contains whiter. The yellow tone is clearer than the cyan tone because it has more own value without adding white. To the value it is possible to be calling him also sheen or luminosity.
The saturation
Slide nº7
A very saturated tone is a very pure color, his mixture contains very few colors. The purest tones and the most saturated, they are the primary ones (yellow, cyan and magenta) because they are composed by an alone color. The secondary ones (green, red and blue) are something less saturated because they are composed by two primary colors. To the saturation it is possible to be calling him also intensity.




The chromatic circle
Slide nº8
To understand and to study the color, the basic colors are placed: magenta, cyan, yellow, red, blue and green in a wheel known by the name of chromatic circle. The chromatic circle is a way of arranging the basic colors depending on his changes of tone. It observes the placement of the colors in the chromatic circle:
- The colors numbered with the number 1
They are primary: magenta, yellow and cyan.
- The colors numbered with the number 2
They are secondary: green, blue and red.
- The colors numbered with the number 3
They are tertiary and are obtained mixing one

Primary with the secondary near one: yellow
+ Green = green yellowish. Cyan + Green = green cyan, yellow +Red = red yellowish, magenta +Red = red magenta (blunt), cyan + blue =
Cyan blue, magenta + blue = blue Magenta.



Finally, I want that you look at this color during a few minutes and later on having removed the image we will see the complementary color.

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