Impactnetworking

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The world surrounding the person, is perceived generally by the color. Color has not only information, but also an emotional component. A human eye — very thin tool, but, unfortunately, color perception subjectively. It is very difficult to transfer to other person the sensation of color.

At the same time for many branches of manufacture, including for polygraphy and computer technologies, more objective methods of the description and color handling are necessary. The numerous color models describing this or that dial-up of parameters are for this purpose developed.

In the program of adobe Illustrator for assignment of color parameters objects can use some color models depending on the task. These models differ by principles of the description uniform color about - странства, existing in the objective world.

Set of colors are visible because that objects, their radiating, are shone. It is possible to carry to such colors, for example, this world ("great wild world"), colors on screens of the TV set, the monitor, film- and slide projectors and etc. Colours a large quantity, but from them it is selected only three which are considered as the cores (primary): it is red, green, dark blue.

At mixing of two primary colors resultant color is clarified: from mixing red and green it turns out yellow, from mixing green and dark blue it turns out blue, dark blue and red give the magenta. If all three colors mix up, the white is as a result formed. Such model of color is additive.

The model in which basis the specified colors lie, carries a title of color model RGB — on the first letters of English words Red (Red). Green (Green), Blue (Dark blue).

It is possible to present this model in the form of three-dimensional system of coordinates. Each coordinate reflects the contribution of an appropriate component to specific color to a range from zero to the maximum value. A certain cube in which there are"all colors, forming color space as a result turns out.

It is important to mark special points and lines of this model.

	The beginning of coordinates. All components are equal in this point to zero, radiation misses, and it is equivalent to darkness, hence, began coordinates is a point of black color.
	The point nearest to the spectator. In this point all components have the maximum value that means white color.
	Cube diagonal. On a line connecting the beginning of coordinates and a point, the nearest to the spectator, gray shades are allocated: from black to the white. It happens because all three components are identical and are allocated in a range from zero to the maximum value. This range differently name a gray scale (Grayscale). In computer technologies now are used 256 gradation (shades) of the gray more often. Though some scanners have possibility to encode 1024 shades of gray and above.
	Three peaks of a cube designate pure initial colors, remaining three reflect double mixing of initial colors.

To see and define colors and parameters of this model it is possible on palette Color (Synthesis). The information on a palette look in chapter 8.

This model, of course, is not absolutely customary for the artist or the designer, but it is necessary for accepting and it to understand because with this model the scanner and the monitor screen — two major links in handling of the color information work.

The colors concern the reflected, which do not radiate, and use this world, subtracting from it certain colors. Such colors are called as subtractive ("subtractive") as they remain after subtraction of the cores additive. It is clear that in that case and the main subtractive colors will be three as they were already mentioned: blue, magenta, yellow.

These colors make a so-called polygraphic triad. At printing by colors of these colors red, green and dark blue components of this world are absorbed in such a manner that the most part of a visible color spectrum can be reproduced on a paper. To everyone пикселу in such image the values defining percentage of triad colors (though actually all is much more difficult) are appropriated.

At mixing of two subtractive making resultant color it is blacked out, and at mixing of all of three black color should turn out. At total absence of color there is a white color (a white paper).

As a result it turns out that null values of components give white color, the maximum values should give black, their equal values — shades of gray, besides, there are pure subtractive colors and their double combinations. It means that the model in which they are described, is similar to model RGB.

But the problem consists that the given model urged to describe real polygraphic colors which — alas — it is far not so are ideal, as a color ray. They have impurity, therefore cannot superimpose completely all color range, and it leads, in particular, to that mixing of three main colors which should give black color, gives any indefinite ("dirty") dark color, and it is faster темнокоричневый, than deep black color.

For compensating of this lack black color has been imported to number of the main polygraphic colors. She added the last letter in a title of model CMYK though and it is not absolutely normal: With is Cyan (Blue), the M is Magenta (Magenta), Y — Yellow (Yellow), and (attention!) to is YasK (Black), i.e. from a word the first is taken not, but the last letter (there is also other version: from English word Key (color) — "planimetric (color)").

Thus, models RGB and CMYK though are connected with each other, however their mutual passages each other (converting) do not happen lost-free, as color spanning at them different. Also it is a question only of reducing losses to comprehensible level. It causes of very difficult calibrations of all hardware making operation with color: the scanner (it carries out image input), the monitor (on it judge color and adjust its parameters), the output device (it creates originals for the press), the press (fulfilling a finite stage).

If two above described models (RGB and CMYK) to present in the form of uniform model the sectional variant of a color circle in which colors are allocated in the order known still from school turns out: red (R), yellow (Y), green (G), blue (), dark blue ().

On a color circle primary colors of models RGB and CMY are in such dependence: each color is allocated opposite to (complementary) color adding it, thus it is between colors with which help it is received. For example, addition of green and red colors gives the yellow.

To strengthen any color, it is necessary to weaken color adding it (allocated opposite to it on a color circle). For example, to change the general color score towards blue tones, it is necessary to lower in it the content of red color.

On edge of this color circle so-called spectral colors or color tone (Hue) which are defined by length of the luminous wave which reflected from opaque object or has transited through the transparent object are allocated. Color tone is characterized by position on a color circle and defined by value of a corner in a range from 0 to 360 degrees. These colors possess the maximum saturation, i.e. dark blue цвет*еще dark blue cannot be any more.

The following parameter is color saturation (Saturation) is the parameter of color defining its purity.

Color saturation reduction means it разбеливание. Color with saturation reduction becomes pastel, faded, blurred. On model all equally saturated colors are allocated on concentric circles, i.e. it is possible to speak about an identical saturation, for example, green and magenta colors, and the is more subcentral a circle, the more and more разбеленные colors turn out. At the center any color as much as possible разбеливается also becomes white color.

Therefore operation with saturation parameter can be characterized as adding in spectral color of certain percent of white color.

One more parameter is brightness of color (Brightness) is the parameter of color defining illuminance or затемненность of color. Reduction of brightness of color means it зачернение.

Therefore operation with brightness parameter can be characterized as adding in spectral color of certain percent of black color.

Generally, any color turns out from spectral color adding of certain percent of white and black colors, i.e. actually gray color.

This model already much is closer to traditional understanding of operation with color. It is possible to define at first color tone (Hue), and then a saturation (Saturation) and brightness (Brightness). Such model received a title on per - вым to letters resulted above English words — HSB.

Model HSB will not bad be coordinated with perception of the person: color tone is an equivalent of length of a wave of light, a saturation — intensity of a wave, and brightness — an amount of light.

Lack of this model is necessity to transform it in model RGB for display to the screen of the monitor or in model CMYK for obtaining of a polygraphic print.

Color model L*a*b has been created by the International commission on lighting (С1Е) for the purpose of overcoming of essential lacks of the models set forth above. In particular, this model urged to become hardware-independent model and to define colors without thinking about device singularities (the monitor, the printer, the press and etc.).

In the commission pioneer experimental operations have been performed on learning of perception of color by the person. The huge statistical material allowed to create a series of mathematical models in which color was described not in terms of the elements which are played back by devices, and with usage of three component color sights of the person.

In this model any color is defined светлотой (L) and two chromatic components: in parameter and which changes in a range from green to red, and in parameter Ь changing in a range from dark blue to the yellow.

In the given model also it is difficult to be guided, as well as in models RGB or CMYK, but also it is necessary to know about this model, as the program of adobe Illustrator 9.0 uses it as model-intermediary at any converting from model in model. Besides, it can be used in following cases: at the press on printers with PostScript Level 2 and Level 3, by operation with format PhotoCD, at color image converting in a gray scale.

The traditional gray scale using on each пиксел images one byte of the information, can transfer 256 shades (gradation) of gray color or brightness (brightness): value 0 represents black color, and value 255 — white.

The gray scale can express and in percentage, in this case 0 % white color (represents absence of color on a white paper), and 100 % — black color (a die of deep black color).

At converting of images in gradation gray in a color model each component receives the identical values equal to values of gray shades (as the gray scale is allocated on a diagonal in a color cube of model RGB).

Color can be presented in the nature, on the monitor screen, on a paper. In all cases the possible range of colors, or color spanning (gamut), will be a miscellaneous (fig. 4.8).

Rice 4.8. The Simplified diagram of color spanning of models L*a*b, RGB, CMYK

The broad range allocates a normal human eye, it is much wider than that the colored film (a color slide) can play back.

At a colored film the range is wider, than at the color monitor (at it a problem with pure blue and yellow colors) which in turn has more broad range, than at devices of the color press (at them problems with the colors which components have very low or very high density).

Devices of the color press also can be built in a ruler on color spanning, since the elementary inkjet printers and finishing the most complicated devices of the numeral press.

Proceeding from it to play back in all range a color slide means of the polygraphic press initially exigeant task. One of methods of an output of this of "a desperate situation" are management systems color.