FHT_Colors Definitions and Models

Colors definitions and Models Nabila Ibrahim Abd El – Hamed

William Benigno Barragan Zaque

Colors Definitions and Models


University of applied sciences stuttgart

Department of surveying and geoinformatic

Nabila Ibrahim Abd El – Hamed

National Authority for Remote Sensing and Space Sciences (NARRS),

CAIRO

December 2004

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1 Abstract

Colors have importance in live. The history of the concept of the colors started in 1666, when Isaac

Newton presented his color circle. He demonstrated that light contains all wavelengths of the visible

spectrum. The human eyes can perceive wavelengths, between 350 and 780 nanometers. We can

define the color as a sensation, which occurs when light energy, incident on the retina and is

interpreted by the brain. The principal models that define the colors are: RGB, it is the most common

model which is used in television and computers. It creates the colors by combining different

percentages of three primary colors (red, green and blue). The other model for the presentation of

colors is called CMYK; printing is based on this, which works with the colors Cyan, Magenta, Yellow

and Black. On the other hand HSB model defines the colors by Hue, Saturation and Brightness in

percentages.

Using of the colors has a loot advantages in different fields. In education it is important as a tool for

memorizing and easy reading. The same form is used for abstraction of the important information and

presentation of results.

Keywords:

Color, Newton color circle, wavelength, visual spectrum range, RGB Model, CMY(K) Model, HSB

Model, Primary colors.

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Table of contents

1 Abstract.............................................................................................................................................2

2 Table of Figures................................................................................................................................4

3 Introduction.......................................................................................................................................5

4 Color definition.................................................................................................................................5

5 The human color perception.............................................................................................................5

5.1 Observation of the colors..........................................................................................................6

6 Models that defined colors................................................................................................................7

6.1 RGB Model...............................................................................................................................8

6.2 CMYK Model...........................................................................................................................8

6.3 HSB Model.............................................................................................................................10

7 Applications of the colors...............................................................................................................11

7.1 Satellite Images.......................................................................................................................11

7.2 Education................................................................................................................................11

7.3 Information.............................................................................................................................11

7.4 Presentation.............................................................................................................................11

7.5 To improve abilities:...............................................................................................................12

8 Conclusions.....................................................................................................................................13

9 References.......................................................................................................................................14

10 Glossary of terms......................................................................................................................15

11 Index...........................................................................................................................................16

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2 Table of Figures

Figure 1: Process in the human color perception....................................................................................7

Figure 2: RGB Model..............................................................................................................................8

Figure 3: CMYK Model..........................................................................................................................9

Figure 4: HSB Model.............................................................................................................................10

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3 Introduction

In many areas of the knowledge and in the sciences, the colors are very important. Sensations, animate

status, symbols, emotions … and many situations that are too difficult to understand when doesn’t any

have help of the colors. For example can be used, in communication, smile, gesture and laugh, but if

these expressions are integrate with appropriate color, it is possible that the interpretation of this

expression can be are more real.

It is true that the use of colors is continue. The colors are used in every minute of the normal live of

people.

In the following pages are given description about the physical formation of the colors in the human

vision and the principal models used for the formation the Them.

4 Color definition

When we speak about colors it is necessary to speak about Isaac Newton who made a study of color

starting at the age of 23 in 1666 and developed the useful Newton color circle which gives the insight

about complementary colors and additive color Theory. We can consider that his contribution was the

idea that white light contains all wavelengths of the visible spectrum. He demonstrated this fact with

experiments on the dispersion of light in glass prisms. This is the basis to Know that the light is a form

of electromagnetic radiation.

Electromagnetic energy travels as waves characterized by their frequency and their wavelength. The

electromagnetic spectrum includes energy that the human eye can not perceive for example: radio

waves, or infrared, but there is a part of the electromagnetic spectrum that our eyes can perceive,

visible spectrum, between 350 and 780 nanometers (nm) is called light. Distinct frequencies are visible

as distinct colors.

We can define color as a sensation, which occurs when the brain interprets light energy, incident on

the retina.

5 The human color perception

Our eyes have three sets of sensors, called cones with peak sensitivities at light frequencies that we

called red (580 nm), green (540 nm) and blue (450 nm). Light at any wavelength in the visual

spectrum range, will excite one or more of these three types of sensors. Our perception of which color

we are seeing is determined by which combinations of sensors are excited and by how much.

Wherever color can be represented as a combination of the three primary colors.

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5.1 Observation of the colors

Figure 1 show 8 steps for the observation of the colors.

1. The most important thing for the formation of the colors in the brain is the light that can be

produced of natural form by the sun or the artificial form by the normal lamps.

2. The second step is the transitions of the energy in three different wavelengths, which represent

the colors: red, green, and blue.

3. The object that we see absorbs some wavelength, according to the composition of this object.

4. The wavelength that the object doesn’t absorb is reflected.

5. The human eye receives the information of wavelength that is reflected by the object.

6. The retina of the human eye transmits the information to cones.

7. The cones can identify the color of the object.

8. It is possible to see the object according to its color.

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Figure 1: Process in the human color perception

6 Models that defined colors

The are thee different models to define colors:

RGB Model: This model uses the colors red green, and blue, and the colors are defined by percentage

of those colors.

CMY(K) Model: This model uses the colors cyan, magenta, yellow, and black, and the colors are

defined by percentage of those colors.

HSB Model: The color are defined by their Hue Saturation Brightness: with the HSB model, all

colors can be defined by expressing their levels of hue, saturation, and brightness, in percentages.

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6.1 RGB Model

This model is the most important for the computers and television because they create the colors based

on RGB model. Monitor and television can create millions of colors by combining different

percentages of three primaries, red, green and blue. While using the image processing software like

“Photoshop” you can see that these RGB colors are added with the help of numerical value, that is

possible to identify from 0 to 255 different values. Figure 2. With RGB, mixing of red and green

equally gives yellow, mixing of green and blue creates cyan and the mixing of red and blue creates

magenta. When all the three colors, red, green and blue are mixed equally they produce white light.

Hence it is called Additive color model. Another RGB model based example is the human eye itself

and scanners.

The basic advantage of RGB model is that it is useful for full color editing because it has wide range

of colors. But at the same time this model is said to be device dependent. It means that the way the

colors are displayed on the screen depends on the hardware used to display it.

Figure 2: RGB Model

6.2 CMYK Model

Printing inks are based on this model, CMY is opposite model of RGB. With the full presence of

cyan, magenta and yellow we get black. But practically in the printing industry it is impossible to

create black with these three colors. The result of the mixture of CMY is muddy brown due to the

impurities of the printing inks. Hence black ink is added to get solid black. The outcome of this

process CMYK model and k stand for black color, which is also recognized as 'key' color. Since black

is a full presence of color, you will have to subtract the levels of cyan, magenta and yellow to produce

the lighter colors. This can be explained in different way. When light falls on the green surface or

green ink, it absorbs (subtracts) all the colors from light except green. Hence the model is called

subtractive model. Print production is based on this model. Figure 3

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Figure 3: CMYK Model

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6.3 HSB Model

Color can be described conceptually by a three-dimensional HSB model:

Hue (H) refers to the basic color in terms of one or two dominant primary colors (red, or blue-green,

for example); it is measured as a position on the standard color wheel, and is described as an angle in

degrees, between 0 to 360.

Saturation, sometimes called chroma, is the strength or purity of the color. Saturation represents the

amount of gray in proportion to the hue, measured as a percentage from 0% (gray) to 100% (fully

saturated). On the standard color wheel, saturation increases from the center to the edge.

Brightness (B) refers to the color’s proximity to white or black, which is a function of the amplitude of

the light that stimulates the eye's receptors; it is also measured as a percentage - if any hue has a

brightness of 0%, it becomes black, with 100% it becomes fully light. Figure 4. You can use the HSB

model in Photoshop to define a color in the Color palette or Color Picker dialog box, but there is no

HSB mode available for creating and editing images.

Figure 4: HSB Model

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7 Applications of the colors

7.1 Satellite Images

Colors can be used in Satellite Images. It is possible to make different combination between colors and

bands of the images, in order to identify, resources, different concentrations of materials, different

heights etc. Some commons applications are:

In Geological applications for Mineral Exploration and Monitoring Miens.

In Digital Elevation Models, for observations of Slop Aspect.

In agriculture applications for identify different types of vegetation.

Marin Applications for Detecting the Bottom of the See & its inhabitance.

Climate Applications for Real Time Data for Monitoring Hurricanes.

7.2 Education

For more complex tasks like reading, memorizing, drawing conclusions, or deciding the effect of color

cannot as easily proven. The color can be used in pedagogical process specially in the primary school,

for to teach to the children.

7.3 Information

The use of colors can effectively support human performance in visual image interpretation

processing. When colors are used correctly the interpretation of information is easier.

7.4 Presentation

Even if this is not the case, users find colors more pleasant, more aesthetically pleasing, inspiring or

useful than a monochromatic presentation. Colors can increase the users' self-assurance to find their

way around and to find the information they are searching for.

.

7.5 To improve abilities:

Separating figure from ground, that is, separating the important from the less important.

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Discerning the inner structure of objects, finding groupings.

Searching, discovering, and localizing objects.

Recognizing and remembering.

.

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8 Conclusions

Colors have a fundamental physical base in the electromagnetic spectrum. It permits to classify the

kind of electromagnetic energy the human eye can identify. The human eyes can identify the colors

by sensors called cones. These sensors are sensitive at light frequencies for the three primary colors

red, green and blue.

The observation of the colors is a process where there are interactions between factors as: light,

wavelengths, object, the retina of the eye and the brain.

There are three models to define colors, each of them use different techniques and methods. The most

common model is used in television and computers, and is called RGB, this works with a combination

of three primary color (red, green and blue).

There are two models, the first one is CMY(K) that use the colors (Cyan, Magenta, Yellow and Black)

and the second one is HSB (Hue, Saturation and Brightness) it woks with saturation and brightness.

These models are very important in cartographic, topographic and engineering applications, also is

used for software like arc-view and geomedia.

The most important think is that every model define each white color precision, because presents one

numerical value for each color to make then unique and unrepeatable.

Color is important in several fields of knowledge and science existing a good integration between high

technology and human resource to apply then in real problems and looking for new alternatives for

explorations to improve life conditions.

Colors are very important in some areas as education, information and communication, because make

easier understand the information around us, also can represent sensations and express sentiments.

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9 References

Theory perceive the color, introduction to graphic of computer

http://semmix.pl/color

Remote Sensing Tutorial http://rst.gsfc.nasa.gov

USGS: Earthshots http://www.usgs.gov/Earthshots

World of Beams http://cbp-1.lbl.gov

R.M. Boynton, Human Color Vision, Special Limited Edition, Optical Society of America,

Washington D.C., 1992. R.W.G. Hunt, Measuring color 3rd Ed., Fountain Press, England,

1998.

M.D. Fairchild, Color Appearance Models, Addison-Wesley, Reading,

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http://cbp-1.lbl.gov/

http://www.usgs.gov/Earthshots

http://rst.gsfc.nasa.gov/

http://semmix.pl/color



10 Glossary of terms

Brightness -- the perceived intensity of the light. Intensity is the radiant energy emitted per

Chromacity -- the purity and dominant frequency of a light grouped

unit time, per unit solid angle, and per unit projected area of the source.(ex.: light vs. dark red)

Complementary colors -- two colors that when combined produce white light. (ex.: red - cyan, green

- magenta, blue - yellow).

Hue -- The "color" of a color specified by the dominant wavelength also called the dominant

frequency, (ex.: "red" vs "green"). This is the most obvious dimension of a color and identifies a color

by name, i.e., red, yellow, blue. Every color falls into a definite hue category.

Luminance or Value -- the total power of the light determines the "lightness" of a color (ex.: light vs.

dark red). Brightness (radiant energy) is related to the luminance of the source

Primary colors -- the two or three colors used to produce other colors in a color model.

Saturation or Purity -- the "colorfulness" of the color (ex.: vivid red vs. dull red). Purity describes

how washed-out or "pure" (vivid) the color of the light appears. Pastels and pale colors are described

as less pure.

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11 Index

Brightness.................................................................................................................................................7

CMYK Model...........................................................................................................................................8

colors.........................................................................................................................................................5

HSB Model.............................................................................................................................................10

Hue............................................................................................................................................................7

Information.............................................................................................................................................11

models.......................................................................................................................................................7

perception..................................................................................................................................................5

Presentation.............................................................................................................................................11

RGB Model...............................................................................................................................................8

Saturation..................................................................................................................................................7

spectrum....................................................................................................................................................5

To improve abilities................................................................................................................................12

To learn...................................................................................................................................................11

wavelength................................................................................................................................................6

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FHT_Colors Definitions and Models

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