The eight color knowledge of printing:
1. Consistency of color. An important way to ensure color consistency is to allow customers to observe color proofs and printed proofs under standard lighting conditions and obtain their approval. In order to reduce the color change in the process of transmission and reproduction, the printing industry has specially formulated standard color observation conditions, that is, standard color observation pool (a light source control area with a stable environment set for observing proofs or other printed products).
There are two key elements of this color observation cell: one is lighting (color temperature is 5000K); the other is neutral gray environment (MunsellN8).
It is very important to check the color on the observation pool, because the lighting conditions and surrounding environment when we check the color will affect our perception of color. If there is no standard observation pool, then we can also view the proofs under indirect sunlight.
2. The influence of lighting. When we observe the color under different lighting conditions, the effect we see is also different. Another issue we need to pay attention to when observing colors is metamerism. The so-called "metamorphism" means that when two proofs are under a certain light source, the colors presented are the same, while under another light source, the colors presented are different.
When observing colors, it is very important to keep the lighting conditions stable and consistent. The reason why we choose a light source with a color temperature of 5000K is mainly because this light source is a mixture of red light, green light and blue light, which can provide people with a stable and consistent observation environment.
3. The impact of the surrounding environment. Do we observe the surrounding environment when printing proofs will affect the color? Nearby colors, that is, colors that are close to the proof or printed sheet that is being observed can affect people's perception of color.
This is the so-called "critical effect", and it reflects to a certain extent the importance of using a neutral environment when observing proofs. It is understood that the use of standard gray paint (MunsellN8) in the surrounding environment can effectively reduce the influence of neighboring colors that people suffer when confirming colors.
4. Paper. The subtractive color method refers to a method of mixing colors with yellow, magenta, cyan, and black inks in a white environment (usually paper). In this color reproduction process, there is an element that will have a major impact on the color of the machine printing effect, that is, paper.
The same ink color may produce different printing effects on different papers. The whiter the paper, the larger the color gamut that can be reproduced on the printing press. If the Baidu of the paper is not enough, then the color gamut it reproduces on the printing press is relatively small.
5. Spot colors. Each spot color corresponds to a special ink (except yellow, magenta, cyan, and black), which needs to be printed through a separate printing unit on the printing press. There are many reasons why people use spot colors in prints. Highlighting a company ’s brand image (such as Coca-Cola ’s red or Ford ’s blue) is one of them. So, can you accurately reproduce a spot color whether it is for customers or It is critical for printing houses.
Another reason may be the use of metallic inks. Metallic ink usually contains some metallic particles, and can make the printed matter show metallic luster. In addition, when the color requirements of the original design exceed the gamut range that can be achieved by yellow magenta, black, we can also use spot colors to supplement.
6. Convert colors to CMYK. When we convert the color of an image from RGB to CMYK, usually two methods are used to generate halftone dots of black ink, one is under color removal (UCR), and the other is gray component replacement (GCR). Which method to choose depends mainly on the amount of yellow, magenta, cyan, and black inks to be printed in the image.
"Background removal" refers to the removal of a portion of the primary colors of yellow, magenta, and cyan to form a neutral gray background color, that is, the nearly black background color formed by the superposition of the three primary colors of yellow, magenta, and cyan, and replaced by black ink . The background color removal mainly affects the shadow area of ​​the image, not the color area. When the image is processed by the method of removing the background color, it is easy to appear color cast during the printing process.
The gray component substitution is similar to the background color removal. Black ink is used to replace the gray formed by the color ink overprinting, but the difference is that the gray component substitution means that the gray components in the entire tone range can be replaced with black. Therefore, when the gray component is replaced, the amount of black ink is very small, and the image is mainly printed by color ink. When the maximum amount of replacement is used, the amount of black ink is the largest, and the amount of color ink is reduced accordingly. The image processed by the gray component replacement method is more stable in the printing process, but its effect depends to a large extent on the ability of the printing press operator to adjust the color.
7. Professional terminology. The reason why we think color is difficult to describe is mainly because it is a feeling, just like smell, taste and hearing, this feeling cannot be described in words. When we have to use words to describe colors, we often use vague words such as "flat", "turbid", "too warm" or "too cold".
For example, what is an image that is too warm? Does it mean its color is reddish, yellowish, or magenta? What does "too cold" mean? Does it mean that the color of the image is too blue, too green, or too green? When we say that the image is too "flat", it usually means that its contrast is not enough, and the "turbid" consciousness means that the color tone of the image is too dark. The use of non-standard terminology will prolong the proofing cycle, thereby delaying the production schedule of live parts. Therefore, we must use professional terminology when talking about colors-this can save you a lot of time and money.
8. Printing is not a "complete match" process. What is replication? Replication is not an exact match, but is infinitely close. Printing is not a complete matching process, mainly because there are many color reproduction systems in the color reproduction process. Photography is a typical color reproduction system, as is proofing and printing.
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