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application of color transmission and reproduction in cosmetic tube design

2021-11-18

Cosmetic tube design usually focuses on color composition and innovation while ignoring the importance of color transmission and replication, which may lead to various problems in the replication of design works. In this paper, the cosmetic tube manufacturer introduces the key theory of color transmission and reproduction from three aspects of chroma space, rasterization and reproduction process, and discusses the application of the theory in the design of cosmetic tube with practice. It aims to improve the quality and efficiency of cosmetic tube design and reduce the cost and failure rate of cosmetic tube product replication.


The color of cosmetic tube is the main element and way to carry and express the design idea of cosmetic tube, and it is an important method and tool to convey the information of cosmetic tube. In the process of transmission and replication from digital media to paper and ink media, the chroma space and color medium in the color have undergone qualitative changes, which can easily lead to color deviation between the product and the original manuscript, thus deviating from the intention and original intention of the design of cosmetic tube. In order to guarantee the consistency of color between product and design manuscript, it is necessary to analyze and compare the key theories of color transmission and replication of cosmetic tube, and study and discuss its application in cosmetic tube design practice, in order to improve the efficiency and quality of cosmetic tube design.

One, the color space of the cosmetic tube

The concept of "chromaticity space" was introduced so that color could be represented and measured. Chromaticity space is not unique, there are at least ten kinds of chromaticity space. Cosmetics tube design commonly used chroma space RGB space, CMYK space, Lab space.

1. Dimension of chroma space of cosmetic tube

For cosmetic tube wholesale, the dimension of chromaticity space refers to the number of variables required by the chromaticity space to represent color. The dimensions of the three commonly used chromaticity Spaces mentioned above are: RGB-3; CMYK - 4 d; Lab - 3 d. RGB chromaticity space is the space commonly used in original design, and CMYK chromaticity space is the space used in output copy. From cosmetic tube design to production, color must be converted from RGB space to CMYK space. The mathematical mechanism of this transformation is nonlinear "ascending dimension" mapping. In the design of cosmetic tube, color bitmap should be transferred to CMYK space to complete color correction. For vector images, the colors can be calibrated directly using the values in the CMYK color scale manual. Soft proofing is the conversion process of files from RGB space to CMYK space and then back to RGB space. The CMYK files in the middle must be the files after color separation.

2. The gamut of the chroma space of the cosmetics tube

The gamut of the cosmetic tube refers to the number of colors contained in a chromatic space. The larger the gamut, the more colors the chromaticity space contains and the wider the color range. Vice versa. RGB chromaticity space is the color space of digital display equipment. Each dimension can be assigned 256 gray levels (8bit display), and the color gambit after the combination of the three dimensions exceeds 16.77 million. CMYK is the color space of ink, although the space is more than a dimension of RGB space, in fact, ink color ability and printing equipment performance is limited, CMYK gamut is smaller than RGB gamut, about 80% of the RGB gamut. Cosmetic tube manufacturers should always consider the matching between the gamut of the chroma space used and the gamut of the output device, and adhere to the principle of consistency of the gamut. For example, cosmetics tubes should be designed to avoid using colors outside the CMYK gamut if they are output from a traditional printing press. Due to the large color gamut of digital printing press, if the output of digital printing press, the design color can be appropriately beyond the traditional CMYK color gamut, but also pay attention to match the color gamut of digital printing press.

3. Equipment correlation in the chroma space of cosmetic tube

The device correlation of cosmetic tube chromaticity space refers to whether the appearance of color in the chromaticity space is affected by the performance of the equipment presenting it. For example, the same RGB image file may look different on different computer monitors (even with the same brand and model); In the same CMYK picture file, the color of batch products printed and copied through the cosmetic tube is not exactly the same. Therefore, RGB space and CMYK space are both device-dependent chromaticity Spaces. Lab space is a chromaticity space independent of equipment, known as standard chromaticity space, as the hub and benchmark of color conversion of different chromaticity space. The cosmetic tube supplier should fully master the characteristic file (Profile) of the equipment used in the design work, and embed the characteristic file of the equipment in the design work, so that the production process can accurately grasp the characteristic information of the equipment used in the design work.

Second, rasterization

The color of cosmetic tube design works is usually in digital format, and the color of cosmetic tube products is usually in analog mode of ink dots. There are essential differences between them. Rasterization is the only way to complete the conversion between the two, and is the technical guarantee to faithfully copy the design color into the product color.

1. Cosmetic tube printing resolution and resolution

Resolution is used to describe the fineness of a digital image. It is the number of pixels per inch in an exponential image. Resolution refers to the maximum number of points per inch that a hardware device (scanner, laser imagesetter, CTP plate maker, digital printer) can produce. For example, if the resolution of an output device is 3600DPI, the diameter of the output record point is about 7m. There is no mathematical relation between the resolution of digital image and the resolution of equipment. Before design, we should first understand the type of output equipment and its resolution, and on this basis to start planning the work of cosmetic tube design.

2. Cosmetics tube printing grayscale and dot cell

The gray level of digital image of cosmetic tube printing is 256. In paper and ink mode, the gray level of a single dot depends on the size of dot cell, which means the maximum number of record points contained in a single dot. Obviously, in order to ensure the color distortion free transmission from digital image to paper and ink image, the dot cell size had better be consistent with the digital image gray level (256 gray levels). At this point, the dot cell size should be 16×16, lower than this value, will result in the output of digital image gray level parallel processing, resulting in color information compression distortion.

3. Features of printing dot of cosmetic tube

The cosmetic tube printing dot has three characteristics: dot shape, dot size and the number of network lines. Dot shape refers to the geometric shape of dot, common circle, square, diamond, etc. Dot size is actually the area rate of dot, which means the proportion of the area of the exposed (inked) part to the area of the dot cell, the unit is %. The number of network cables is the number of network dots in one inch, in LPI. There is a fixed functional relationship between the gray level of dot, the resolution of output equipment and the number of network lines, which is expressed by the following formula:

G=(OPI/LPI)2+1

Where, G represents the gray level of a single dot; OPI represents the resolution of the output device; LPI indicates the number of network cables.

In most cases, the default dot shape for output devices is circular, but that doesn't mean circular dots are the best choice. If the image is more dark, it should not choose circular dot, but should choose square dot; If the image has more shallow areas, the circular dot should be selected first. Different color separation plate can choose different dot shape, depending on the color separation layout of the gradient characteristics. When the resolution of the output device is limited, the higher the number of network cables is not the better. If the number of network cables is too high, the gray level of dot will be compressed and the level and tone of image reproduction will be reduced.

Three, cosmetics tube printing replication process

1. Color separation and spot color

Decompose the color information into CMYK four printing plate process called color separation, its essence is the color information from the original chromaticity space to CMYK chromaticity space conversion. Take RGB images as an example. As mentioned above, since the gamut of RGB space is larger than that of CMYK space, it is necessary to understand the gamut of production and replication before the design of cosmetic tube and avoid using colors beyond the GAMut of CMYK. In cases where colors outside the CMYK gamut must be used, a high-fidelity reproduction process or spot color can be used. Cosmetic tube printing and replication is more than the traditional four-color ink printing process, belongs to a higher dimension of color space, need to use a special supporting color separation software for the original image color separation. Cosmetic flexible printing spot color refers to the use of color ink different from CMYK for reproduction process. Each spot color needs to be specially made a plate, printing takes up a unit, is bound to increase the cost of replication. Therefore, spot color printing is usually used in the following three colors of cosmetics tube printing. For high-grade products or well-known brands, in order to improve the identification of product cosmetics tube, you can consider increasing the number of spot color, or even all use spot color printing.

2. Cosmetics tube printing dot increase and compensation

Due to cosmetic tube printing production pressure, ink penetration and other factors, the dot area on the copy is usually larger than the dot area on the original document, this phenomenon is called dot increase. The increase of the dot with an area of 50% is the most obvious, and the increase rate of the dot can reach 35%. With the increase or decrease of dot area, dot increase rate decreases gradually. The dot increase rate of 5% and 95% nodes is basically the same, and the value is about 1%. The increase of dot in cosmetic tube printing will lead to blurred hierarchy and dark color of the duplicated image, so it is necessary to compensate the increase of dot in the design process. For example, suppose that under certain replication conditions, the increment rate of 40% dot is 25%(increased by 10 points), during design, the 50% dot should be lowered to 40%, so that the copied dot is still 50%, which is consistent with the size of the original design dot, so as to ensure the fidelity of color replication.

3. Cosmetics tube printing grey balance and background gain

Grey balance is the basic standard to measure the accuracy of color reproduction. Only when grey balance is accurate, the color reproduction of the whole image can be accurate. Affected by the purity of ink, to get the real neutral gray to improve the amount of green ink (C). For example, to produce 25% neutral ash, the ratio of CMY should be set to 25%:16%:16%. Different brands of ink neutral grey ratio is different, should be determined according to actual measurement. Once the ratio of CMY to neutral ash is determined, the CMY inks in neutral ash can be replaced with black ink (K). In practice, after replacing color ink with black ink, the dark parts of the duplicated image will appear flat and the level of detail is in danger of being lost. For this reason, in the neutral gray area still use part of the color ink to make up for this deficiency, this process is called background gain. According to experience, the setting amount of background gain accounts for about 10% of neutral gray. For example, when copying the above 25% neutral gray, 22.5% black ink (K) and 2.5% color ink (CMY) can be used, so as to save the amount of color ink, but also to obtain a good visual neutral gray.

4. Cosmetic tube printing trap and bleeding

Cosmetic tube printing trap is to make up for the obvious color difference between the two interface colors due to overprinting is not allowed to produce white leakage. There are many vector graphics in cosmetics tube design works, which are most likely to cause white leakage fault, and generally need to be trapped. The principle of processing is that the color of the light side is appropriate to the dark side of the expansion, the expansion depends on the printing machine alignment accuracy, the higher the alignment accuracy, the smaller the trap value, generally 0.1-0.5mm. In the design of cosmetic tube, when the edge of the image coincides with the edge of the paper, blood design is needed. The purpose of bleeding design is to avoid the white edge left on the edge of the image after cutting the product, which will affect the visual effect. The processing method is to design the image boundary out of the cutting line boundary (beyond about 3mm). Imprinting and bleeding are replication technology skills, cosmetic tube designers are the most likely to make mistakes, so it is necessary to pay attention to.

5. Cosmetics tube printing color sequence

Cosmetic tube printing color sequence has a significant effect on color reproduction, but it is the most easily overlooked link. Most cosmetic tube manufacturers use the same printing sequence all year round. On the one hand, they do not realize the importance of printing sequence. On the other hand, changing the printing sequence requires a thorough cleaning of the printing unit, which significantly increases the time cost of printing operations. When designing, we should communicate with the printing company in advance to understand the printing color sequence used by the printing company and whether the printing color sequence can be replaced. We should ensure that scientific and reasonable color sequence printing can be arranged as far as possible according to the selection principle of the printing color sequence.

conclusion

Cosmetic tube design is the first procedure of cosmetic tube manufacturing, which determines and influences the final quality of cosmetic tube products. Cosmetic tube designers should not only put energy and focus on decoration creativity, but also ensure that the designed works can be faithfully copied into products. Cosmetic tube design should take into account the replication link of the back end, try to foresee and deal with the problems that may occur in the replication process, so as to reduce the production cost of cosmetic tube products, improve the effect and quality of cosmetic tube design.


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