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 Spanish - Chinese The Optics Book - Colors Written by:Karen
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In this section:

The Optics Book

Describing Colors
Types of media

9. Interferences & difraction
10. Polarization
11. Quantic Optics

# Young-Helmotz theory

The Young-Helmotz theory gives an explanation on how color vision works.  It states that there are three kinds of cone receptors, one for red, one for green, and one for blue.  When we see the color red, green, or blue, the red, green, or blue receptors will be stimulated most strongly, respectively.  Each color that we see stimulates a combination of these three cone receptors, which in turn signals to our brain the colors that we see.

# Describing Colors

There are so many different colors and shades of colors that a system needed to be devised to differentiate between the different colors.  Albert Munsell invented the Munsell system to measure colors.  Hue is used to discriminate one color from another, for instance red from yellow, or from blue, etc.  There are 10 different Hues in the Munsell system (Red, Yellow, Green, Blue, Purple, and the ones in between).  Each hue has a gradient from 1 to 10, a gradient of 5 being the middle ground.  So 5R represents a color Red which is neither strong nor weak.

To further discriminate between colors, a value is given to a color.  This value describes the degree of whiteness or blackness that a color possesses (0 being black, 10 being white, neither of which can ever be reached).  A pink color, which is a light red, would be represented as 5R8.  The 5R represents the hue measurement, and the 8 above the horizontal line shows that the red color has a high degree of whiteness.

The last part of the Munsell system involves the strength of the color.  Color strength is known as chroma.  Chroma is represented by an even number between 0 and 16.  The number 0 represents no chroma, and is the color gray.  The chroma number is written under the horizontal line of the value number.  The problem involved with Chroma is that chroma steps vary for different colors (because some colors are just stronger than others).

These numbers (value and chroma) are then used to determine the power of the color.  Power is the product of the value number, and chroma number.  A higher power means that the color has a greater effect.  So, the most powerful red, is 5R414, which has a power of 56.