Subtractive color

As a subtractive color mixing, color subtractive color synthesis or physical mixture, the change in reflectance of a color stimulus from the surface of a body by means of remission, or during passage through a medium ( color filter ) is indicated by transmission. If, however, a little added color stimulus to color stimulus, it is called additive color mixing.

In a narrower sense is meant by subtractive color mixture that extreme principle, in which by cascading of three color filters, the diversity of the color space is reproduced.

Physical process and concept

The subtractive color mixing can not be explained by simple reversal of additive color mixing. In contrast to the additive color mixing, a physiological color mixing, it is a purely physical process, also called the physical color mixing, that is independent of the color perception. With the aid of color filters, such as but not color in a paint pot or on a pallet, are mixed, but there is a change in the light spectrum, instead, is seen as a consequence of the altered color stimulus as changed color or a different color valency rather obtained.

The physical process is not subtractive, but multiplicative. The changing spectrum of light is the result of the spectral reflectance levels ( a measure of reflected light) and transmission factors ( a measure of transmitted light ). The product of these reflections or permeabilities with the original spectral distribution (radiation) is called the modified radiation distribution ( color stimulus function φ ( λ ) ). The modified color stimulus function is reduced to less portions of the light spectrum (subtractive = reduction) than the primary. Of the radiation energy is released slightly.

Because same color filter result ever when cascading with another filter different color stimuli, while conditionally same colors ( radiation ) behave exactly the same case of additive color mixing.

The explanation is based on the trichromatic theory and the fact that the cones on the retina of the eye have their maximum sensitivity for those wavelength ranges of light, which we assign the color sensations Blue, Green and Red: If in the above arrangement, the color filter yellow, magenta and cyan -rayed with neutral white light can be filtered out by absorption spectral complementary color. When yellow filter, for example, the blue area absorbed. The passing range, the blue -sensitive cones stimulate little or no and is therefore registered by the eye as yellow. Absorb the yellow and cyan filters together the blue and the red. The green area for which the eye has its own type of cone can happen. Where the magenta filter to come, the achromatic color black is perceived, because it absorbs the yet transmitted the green area. Outside the filter passes the unaffected original light and caused an eye on the performance of high brightness, ie, the perceived color white.

The colors of the filter, the top of the image of yellow, magenta and cyan, are used as primary colors of subtractive color mixing, the color produced as a secondary color, here blue, green and red designated.

Applications

Body colors

Absorb dyes (ingestion ) certain light waves and reflect the rest. Since the body surfaces are not equal or not equal smooth rough generally, the color stimulus changes in addition, because the light scattering is different.

Filter colors

Color printing and photos on paper

Printing the transparent ink layers of cyan, magenta and yellow (Yellow) (CMYK - process, for example, the ink jet printer ) is placed on a white substrate one above the other. Of the light spectrum changing process thereby takes place both before and after reflection on the surface.

Even when colored paper photo are transparent layers of color that follow the contours of the image content, one above the other on a white surface.

Color film

The color films lie on a crystal clear carrier film over each other transparent layers of paint. You change the tonal range of the translucent light. The principle is both the negative film and slide film when the subtractive color mixing. On the negative film are the "negative" colors, these are the complementary colors generated in the follow-up process on paper image "right" image colors. The "right" are already " mixed " picture colors on the slide film.