What is the additive color effect and what is the subtractive color effect?

Additive color effect, also known as additive color mixing, additive color method (the method of using additive color effect). Monochromatic light (only red light, green light, blue light) synthesizes the visual effect of polychromatic light. Additive color effect is the theoretical basis of color synthesis.

The color lights are added in equal amounts, red light + green light = yellow light, red light + blue light = magenta light, green light + blue light = cyan light. Red light + green light + blue light = white light.

The color lights are added in different amounts, more red light + less green light = orange light, more red light + less green light = red light, more green light + less blue light = green cyan light. By changing the mixing ratio of the three primary colors of red, green and blue (addition of unequal amounts), other colors can be obtained. And with the addition of the color light, the brightness increases accordingly, so it becomes an additive color effect.

One of the color process of photography is the color process of additive color effect. Early color photos, color printers, and color magnifiers were designed and manufactured by the additive color method.

Subtractive color effect, also known as subtractive color mixing, subtractive color method (method using subtractive color effect). Subtracting monochromatic light (only red, blue, and green light) from white light (multi-color light) becomes the color vision effect of another color light. The subtractive color method is not to subtract one primary color from daylight (consisting of three primary colors) to leave two primary colors, but to subtract one complementary color from daylight to leave one primary color. Because a complementary color is composed of two primary colors (three complementary colors are the complementary colors of the three primary colors, and any primary color of the three primary colors is complementary to the mixture of the other two colors). Because green + blue = cyan, red + blue = magenta, red + blue = yellow, so white (red + green + blue)-cyan (green + blue) = red, white-magenta (red + blue) = Green, white-yellow (red + green) = blue. This simplifies the color process. The three complementary colors of yellow, magenta, and cyan can be mixed in different proportions to obtain countless colors. The mixed color is darker than the original, that is, the brightness is weakened, so it is called the subtractive color method.

Different objects have the characteristics of reflecting and absorbing different colors of light. This is because different objects have different molecular structures (such as pigments), different densities, and different surface smoothness. The object is red because it can reflect red light and absorb other colors; the object is green because it can reflect green light and absorb other colors; the object is blue because it can reflect blue light and absorb other colors.

According to this principle, the filter can get the color light we want from the white light. One of the photographic color process is the color process of subtractive color effect. In photography practice, a white light (multi-color light) lamp is covered with a red cover to give out red light, instead of adding red to the white light, it is not additive but subtractive. Because there are three primary colors of red, green, and blue in the white light, the red cover can only transmit red light, while the green and blue light are filtered out. The white light lamp covers what color the cover will show what kind of light, just like the lens plus the color filter, it uses the subtractive color method.