Silk screen printing plate making process (9)

b. Shade addition method. Two or more kinds of color light, mixed to produce another method of color, known as color light color method, also known as color light color mixing method, add color method. The experimental results show that the following color lights can be obtained by mixing the two color lights in equal amounts:

Red light + green light = yellow light;

Red light + blue violet = magenta light;

Blue violet light + green light = blue light.

When the three primary colors of light are mixed in equal amounts, white light can be obtained, as shown in FIGS. 7-10.

The experiment also tells us that if the three primary colors of light red, green, blue and purple were added with three colors of cyan, magenta, and yellow, white light could be obtained.

Red light + blue light = white light;

Green light + magenta light = white light;

Blue violet light + yellow light = white light.

When two colors add white light, we call the two color lights complement each other, that is, the red light and the blue light are each complementary light; the green light and the magenta light are each complementary colors; the blue and yellow lights are mutually complementary. Fill light. The three colors of cyan, magenta, and yellow are called the complementary colors of the three primary colors of red, green, and blue, respectively, as shown in Figure 2-78.

c. subtractive color method. When the method subtracts a certain color light from white light, it can obtain the complementary light color of the subtracted light, such as:

White light - red light = blue light;

White light - green light - magenta light;

White light - blue violet light = yellow light,

Cyan, magenta and yellow are also called three subtractive colors.

The experimental results show that when the white light shines on the yellow filter, the yellow filter absorbs the blue-violet light in the white light, and the red light and the green light, the result of the addition of the red light and the green light, gives us a feeling of yellowness. . When white light is applied to the magenta filter, the green light in the white light is absorbed, and the red light and the blue-violet light are passed, and the result of the addition of the red light and the blue-violet light gives us a feeling of magenta.

When white light shines on the green filter, the red light in the white light is absorbed, and green light and blue-violet light, green light and blue-violet light are added together, giving us a feeling of blue.

If white light is applied to a group of color filters of yellow + magenta, the green and blue-violet light in the white light are respectively absorbed by the color filter, and red color can be obtained. When the white light is applied to the magenta and cyan filters, the red and green light in the white light are respectively absorbed by the filter, and a blue-violet color can be obtained. When white light irradiates a group of color filters of green+yellow, the red and blue-violet light in the white are absorbed by the color filter respectively, and green color can be obtained. When the sun shines on the yellow, magenta and blue group of three filters, the red, green, and blue-violet light are absorbed, and what light does not pass through becomes the ink color.

From the above experiments, we can know that with different proportions of the magenta, yellow, and cyan subtractive color materials, they can also be obtained in various colors. Therefore, we call magenta, yellow, and cyan three primary colors. This method of subtracting colors to add a composite color is color subtractive, as shown in Figure 2-79.

Chromatic additive method and color subtractive method are two opposite concepts, the main difference is: additive method means that the three primary colors of light (red, green, blue-violet) add to white light or two kinds of color light add, A color synthesis method that obtains a new color light that is much brighter than the original color. The subtractive method is a method of synthesizing the colors of the three primary colors (yellow, magenta, and cyan) of a pigment, or adding any two colors to obtain a new color that is much darker than the original color.

In the additive method, the complementary color lights are added to white light; in the subtractive color method, the complementary hue is added, which is approximately black.

There is a complementary relationship between the three primary colors of light and the three primary colors of the pigment. The hue of the pigment three primary mirrors is the hue exhibited by subtracting one of the three primary colors in the white light. Therefore, the hue of the blue-violet, green, and red color filters can be used to check the color separation of the camera to obtain yellow and magenta colors. , blue color negative film, then remake or copy into a positive film.

2 color separation principle. Separation refers to the use of white light to illuminate continuous drafts or transparencies, and reflects or transmits light of different colors to or from the filters. The color light, which is complementary to the filters, is absorbed by the filter, and other colors are filtered. Film, make the film photosensitive, and then develop, fix a color separation film.

The function of the color filter is to transmit the same true color light as the color filter and absorb the other two color lights in the three primary colors of the color light. In this way, there is only one color light sensation on the photosensitive sheet, and the other two kinds of color light are absorbed and cannot be sensitized. The two colors that cannot be sensed are the complementary colors of the hue of the filter, that is, one of the three primary colors of the pigment, so as to obtain the required number of negative films, as shown in Fig. 2-80.