Additive color

The additive color mixing, whether additive color synthesis and color mixing is a physiological phenomenon which is the change in the perceived color impression of the eye by successively adding each of the other color stimulus describes ( = additive adding ). Basically, the color vision using different color-sensitive sensors is in the eye an additive mixture. Since the additive color mixing takes place principally in the eye and brain, it is also called physiological color mixing.

If, for example, the three primary colors red, green and blue ( hence in a suitable brightness) adds " uniform ", the color sensation arises white. The sensation is black, if the sum is zero (no light). The sum of two primary colors produce the sensations of yellow, cyan and magenta.

The creation of local or close in time lying color stimuli is already called additive color mixing, although the effective mixing process takes place only in the eye and brain:

• Close bunch of differently colored light sources (for example, on screens or monitors) or splashes of color (for example, on images in the painting technique of pointillism ); a tight bundle is perceived as a unit, not as a plurality of light sources or multiple swabs,
• Rapid temporal change colored surfaces ( for example, when color top )
• Simultaneous illumination of a diffusely scattering screen with different colored light sources; It is a narrow bundle limiting case differently colored dots because each point reflects the light of all the sources.

Become spectral subregions from the light of the sources taken away (more precisely, reduced in intensity), it is called subtractive color mixing (subtractive = taking away ). Subtractive color mixing is also called Physical color mixing, because it is purely representational in contrast to the additive color mixing does not take place in the eye and brain.

Operation

The additive mixture is described by the three-color theory of Thomas Young and Hermann von Helmholtz. A typical example is the pixel in screens ( TV, computer). The image is composed of many small surface elements. Thus, the three basic colors red ( orange-red ), green, blue ( violet-blue ) are "added". In sufficient distance, this surface element radiator form on the retina of a "mixed" color stimulus, they form a uniformly perceived hue.

Three projectors (headlights ) illuminated with light colors in each of the three primary colors of R ( ed), G ( reen) and B ( lue) a white surface. The color cone may thereby partially overlap. Each projection light appears in its pure color as long as it hits alone on the screen. To overlap two light cones, so arise secondary colors, the colorful primary colors yellow, magenta ( magenta) and cyan ( cyan ). In the center overlap all three cone of light - you see the tertiary color white, the definition white background. The achromatic color black is represented by the darkness in the room. By controlling the intensity of light radiating any shade can be mixing to the area of ​​overlap of all three primary colors. An overlapping triangles will appear colored shadows.

Areas of application

The additive color mixture is the basis of the color reproduction process, based on the RGB color space. Applications consist in particular in monitors, as in color television. The digital photography is based on this form. Depending on the color imaging techniques, different height are used as the grain raster, the line screen or the lenticular method. The technical problems of color reproduction based primarily on the availability of economically, technologically and technically suitable phosphors with corresponding luminescence excitation in the required range. The description of colored areas on web pages can be implemented by an appropriate indication of the proportions of the primary colors in web colors.

In technical systems, the additive color reproduction will be described with different three-dimensional color models. The aim is this possible the " usual nature of the user ," the natural LMS space to adapt. By adding lights (ie, four-dimensionality ) of the (technical) reproducible color space can be improved. This possibility for the first time chose Sharp 2010 its LCD televisions. A fourth phosphor with the previous RGB pixels, red, green, blue phosphor dots, yellow sub-pixels are ( RGBY ) installed for the color mixing. Through mathematical conversions this (extended) light dots can be controlled. The technical goal is the improved play of the critical yellows, golds and browns and skin tones. This rendering problems based on the limited (here) availability of economically viable phosphors, not ready with which the "ideal" primary colors.

In contrast to the mixture of " color lights " is the subtractive color mixing of the mixture of the body colors, such as the color-imparting effect of the analog photograph and the four-color printing is achieved.