Discussion on the influence of ink layer thickness on color rendering effect (2)
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For the same color mixture, when the thickness or the brightness of the illumination source changes, the hue, brightness, and saturation change. In this paper, through the experimental study of the change of pigment concentration (thickness), the coloration phenomenon of the same ink at different thicknesses is analyzed to investigate the effect of the thickness of the ink layer on the coloration effect.
2, the relationship between color mixing and volume
The color mixing matching experiment conducted by the International Commission on Illumination (CIE) shows that when the brightness ratio of the three primary colors is 1.0000:4.5907:0.0601, the white light can be matched, so CIE selects the unit of the three primary colors of red, green and blue. Quantity, ie (R) + (G) + (B) = 1:1:1. Although the brightness values of the three primary colors are not equal at this time, CIE treats the brightness value of each primary color as a unit, so the red, green, and blue primary colors in the color-added color method are mixed in proportion to white light, and the expression is (R) + (G) + (B) = (W). Red light and green light are mixed in proportion to obtain yellow light, that is, (R) + (G) = (Y); similarly, (R) + (B) = (M); (G) + (B) = (C ).
In the color material subtractive method, according to the theoretical analysis, regardless of the color cast, impure and other factors, the three primary colors of cyan, magenta and yellow are mixed to obtain black, that is, (C)+(M)+( Y) = (Bk). The yellow and magenta are mixed in equal amounts to give red, ie (M) + (Y) = (R); the same is (C) + (M) = (B); (C) + (Y) = (G). Therefore, for the red color material, it can be considered as a mixture of yellow color material and magenta color material, that is, (R) = (M) + (Y); the same green color material has (G) = (C) + (Y); The blue colorant has (B) = (C) + (M). Thus, when analyzing the principle of color rendering, the color of the color material can be represented by the primary color.
3, color analysis of color
The essence of object coloring is that the object selectively absorbs the complementary color component of the incident light to reflect (or transmit) the remaining color light to the human eye. We know that red objects appear red under white light, that is, red objects absorb green light and blue light in incident light (white light), and reflect (or transmit) the remaining red light to appear red. In order to better explain this phenomenon, the transmission of the ideal color filter can be analyzed. It is assumed that 1 unit thick primary color material can completely absorb 1 unit of complementary color light, and the rest of the color light is completely transmitted, then 1 When the white light of each unit is incident on the red filter of different thickness, the color of the color filter is as shown in Fig. 3. The expression is as follows:
11 units thick red filter: {(Y)+(M)}→pure red
21/2 unit thick red filter: {1/2(Y)+1/2(M)}→1/2(R)+1/2(W) Light red
As the thickness of the red filter decreases, the color change also changes from pure red to light red, the brightness becomes large, and the saturation decreases sharply.
4, color mixing
The two colorants are mixed, and the color presented varies greatly depending on the concentration (thickness) of the toner. The ideal red color filter and the green color filter are stacked together, and when one unit of white light is incident, different colors appear as the color filter changes. The color rendering process is shown in Figure 4, and the expression is as follows:
1 1 unit thick red filter and 1 unit thick green filter are laminated:
{(Y)+(M)}+{(Y)+(C)}=2(Y)+(M)+(C)→(Bk) black
2 units of thick red filter and a unit of thick green filter are laminated:
{1/2(Y)+1/2(M)}+{1/2(Y)+1/2(C)}=(Y)+1/2(M)+1/2(C)→ 1/2 (Y) yellow
A 3 unit thick red filter and a unit thick green filter are laminated:
{1/4(Y)+1/4(M)}+{1/4(Y)+1/4(C)}=1/2(Y)+1/4(M)+1/4( C)→1/4(Y)+1/2(W) light yellow
The color mixture is darker in color. When the color concentration (thickness) is large, the color is black, and the saturation is 0. As the concentration (thickness) decreases, the color gradually appears, the brightness becomes larger, and the saturation increases rapidly. After reaching a certain level, it gradually decreases.
5, the mixture of color and primary color
The color mixture is mixed with its complementary color material to exhibit color reduction, and the phenomenon that the intermediate color and the non-complementary color primary color material are mixed and colored is more complicated. Taking the ideal combination of the red filter and the yellow filter as an example, when one unit of white light is incident, the color process is as shown in FIG. 5, and the expression is as follows:
a) 1 unit thick red filter and 1 unit thick yellow filter are laminated:
{(Y)+(M)}+(Y)=2(Y)+(M)→(R) red
b) The unit of thick red filter and the unit of thick yellow filter overlap:
{1/2(Y)+1/2(M)}+1/2(Y)=(Y)+1/2(M)→1/2(R)+1/2(Y) Red and yellow
c) A unit of thick red filter and a unit of thick yellow filter are laminated:
{1/4(Y)+1/4(M)}+1/4(Y)=1/2(Y)+1/4(M)→1/4(R)+1/4(Y) +1/2(W) light red yellow
The color mixture is mixed with the non-complementary color primary color materials. As the concentration (thickness) is different, not only the brightness and saturation change, but also the hue changes. When the mixed color concentration (thickness) is large, the color is mixed. The hue, when the concentration (thickness) is decreased, becomes a mixed hue of the intermediate color and the primary color.
Conclusion
In summary, for the same ink, the color properties may change when the thickness of the ink layer changes, and the effect of the thickness of the ink layer on the color rendering effects of the primary color, the intermediate color, and the complex color ink is also different. Especially for the same color mixture, when the thickness is changed, the phenomenon of hue, brightness and saturation will change, that is, the phenomenon of inter-color mixing. Similarly, for a certain color mixture color sample (the thickness of the ink layer is constant), when the brightness of the illumination source changes, the change of hue, brightness and saturation will also occur, which is the reproduction of the printed color and the design of the package color. Has a certain guiding significance.