Analysis Of factors influencing the printing quality of Paper Tube Of Biodegradable materials under observation conditions

Analysis Of factors influencing the printing quality of Paper Tube Of Biodegradable materials under observation conditions

 

Observation condition

The appearance of prints and other objects is greatly affected by the conditions under which they are observed. Therefore, all judgments about color must be made under repeatable conditions. To achieve this, everyone involved in color reproduction must use standard observation conditions. The term "standard observation condition" refers to an environment in which the following conditions are carefully controlled:

 

● Color of light source

● Intensity of light source

● The effect of spectral reflection

● Ambient color

● The impact of non-standard ambient light sources

● Visual adaptation of the observer

 

An environment that meets the above conditions can be achieved by the device designed and provided according to ISO3664. Observation racks or tables require regular maintenance to ensure that their condition meets the standards to be maintained. The maintenance schedule should include the following tasks:

 

● All neutral colored surfaces, fluorescent tubes and partitions should be cleaned at least once a month. The cleaning materials used should not cause damage to these surfaces

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● Fluorescent tubes should be replaced after 2000 hours of use.

 

The standard viewing condition light source has a color temperature of 5000K, and some suggest that using the user's viewing condition is more appropriate. This is impractical for two important reasons:

 

(1) It is impractical to combine every possible light source, and (2) the goal of many prints is to coordinate cooperation and synchronize input from people with different roles in their own companies or even in their own countries, and thus in different circumstances. Standard observation conditions ensure that all participants, regardless of where they are assessed, can do so in accordance with the environment at the starting point.

The only time non-standard lighting conditions should be used is when the observation conditions of the main environment have been determined and controlled. A typical example of such conditions is at a retail point, such as a supermarket. The final evaluation of packaging or display materials booked for the supermarket or mall should be carried out under lighting conditions related to the mall environment.

 

For many printing houses, seeking an observation environment that can faithfully represent the color of the original manuscript determines a very troubling problem. A copy of the production copy, in what environmental conditions to check, evaluation is enough standard, there will be no color difference?

 

The light source will change with time and environment, and the object will have different color conditions under different light sources. If we want to produce printed matter suitable for observation under different light sources, the cost and manpower will cause unnecessary waste. Therefore, we must establish an objective and standard environment to ensure that uniform observation conditions can be used throughout the production. [next]

5000K misunderstanding

 

Some manufacturers say that the color matching manuscript light source they use is 5000K color temperature light source, why to the customer there is also 5000K light source environment, the manuscript color is still wrong? In fact, 5000K just describes the color temperature of the light source, does not represent all of the light source, correctly speaking, the light source issued by the D50 standard lighting body is the approved light source index for printing process. Please be sure to know clearly that this light source in addition to the appropriate color temperature, but also have enough color rendering.

 

First of all, the origin of 5000K color temperature is to heat a standard black body that can fully absorb and radiate energy. When the temperature increases gradually, the color of the light source will change accordingly. The 5000K color temperature means that when the black body is heated to 5000K, the color change of its light color will be white. That is, the most ideal white light, the lowest color bias, so the printing process uses this kind of light source.

 

In addition. It's a matter of color rendering. Color rendering refers to the consistency of the color of an object under sunlight and artificial light source. The color of an object presented in sunlight is the most accurate, because the spectral energy distribution in sunlight is the most comprehensive, and can fully express the color of an object (at this time, the color rendering index of sunlight is the highest 100. However, the spectral energy distribution of artificial lighting is different from that of different materials. Daylight is very different, however, even when the artificial white light is illuminated at a body color temperature of 5,000 K, the color of the object is still different from that seen in sunlight. Most of the problem is that artificial light sources often lack certain monochromatic components, and the color rendering index is below 100. The level of color rendering index represents the distortion of the object. But having a high color rendering index does not mean there is no color bias. The color temperature of light source and color rendering should cooperate with each other. Color temperature is the indicator of light source color, while color rendering is the indicator of light quality. CIE D50 standard lighting body is to define the quality of light source hue to be standardized.

 

Standard lighting body and standard light source

The CIE International Association for Lighting Standards defines the following standard illuminators and specifies their spectral energy distribution according to the different color effects of different light sources on objects.

However, the above standard lighting body can be achieved by different combinations of light sources (simulating spectral energy distribution), but different substances have different stability, so C! E recommends a series of standard light sources (artificial light sources) to match the above standard lighting body. [next]

 

ISO3664 standard observation conditions

When it comes to so much information about light sources and illuminating bodies, what is the most ideal color matching environment? The ISO International Standards Certification Association has published the ISO3664 Lighting Conditions for Viewing Color Lenses and Reproductions (the new version is ISO 3664:2000), which refers to the observation conditions in the printing and reproduction process, as shown in the following four points: 1. Spectral energy distribution of illumination source, 2. Luminescence degree and uniformity of illumination source, 3. Observation of environmental conditions, 4. Stability of the lighting environment.

 

In fact, ISO3664:2000 lighting source requirements more stringent, it takes into account the current initiative of the new color imaging technology and typesetting system, but also on the material under different light sources, the problem of isochromatic spectrum to make the formulation of this standard.

 

illumination

Another important factor is that it recommends two illuminance standards for use in the following situations:

1. High illuminance 20001±500IUX- Used to evaluate and compare images, strict evaluation of printing.
2. Low illuminance 5001±25IUX- Used to resolve image darkening details under similar final viewing conditions.

 

Observe the environment

Observation environment may be a link ignored by each printing industry. I believe you must have seen that the observation environment around the workshop is full of many things, such as posters, ink, cigarette packs, mobile phones and so on. Some of the color manuscript places are still next to the window sill, and some are more dusty.

1. Minimize distractions from your surroundings.
2. After entering the observation environment, should not immediately start to judge the printing, so that workers have time to adapt to the environment.
3. No additional light should enter the viewing area (including reflections).
4. There should be no strong colors around (workers' overalls).
5. The periphery of the observation range should be neutral gray and dark color blocks with reflectance less than 60%.

 

In fact, the above is the printing plant should pay attention to the problem, these conditions are just a signal, can be implemented, not only to improve the environment, but also to improve the quality of production, enhance the professional image of the factory. [next]

How to choose the right light source equipment

 

The simplest way is to buy in line with the ISO standard light box, in addition to meet the iSO requirements, more have A variety of light sources to choose from, such as D65, D50, UV, TL84, A, for different industrial needs. When purchasing, please refer to the following points:

 

1. There are many brands of light tubes on the market that indicate sufficient 5000K(unfortunately CIE has not stipulated the application of standard light source for D50 standard light body), but they may not meet the requirements specified by ISO: color temperature 5000K, color rendering index ≥9.
2 panel material as long as it can be close to the ISO limits such as color for gray - can be measured by the ball type spectrophotometer density instrument color index of the surface of the material, close to LAB-50, 0, 0, luminosity to glossometer measurement of its reflectance of 60%.

 

Test mode

We generally measure the change of color temperature during production is sufficient, because the stability of the lighting body will change with time and environment. There is a cheaper way to check the color temperature on a daily basis. GATF/RHEM sticker (GATF, sold by the Hong Kong Society of Printing Arts) is a kind of sticker. When we place the sticker in the observation environment, it will warn the operator if the color temperature changes. [next]

 

Heterochromatic phenomena in color printing

Metamerism is a universal phenomenon in nature. Simply put, metamerism refers to colors that look the same in appearance, but have different spectral compositions. In other words, two color samples have different spectral reflection curves, but have the same visual effect when illuminated by a certain light source.

 

Isochromatic spectrum color exists in the field of color reproduction, and the problem of color matching is often encountered in the work, that is, the requirement of matching the same color as the sample. It is difficult to achieve the same color appearance, its spectral characteristics are the same, so most of the color is different spectrum.

 

The colors used in the process of color printing can not be exactly the same as those used in various color manuscripts, such as traditional Chinese painting pigments and watercolor pigments used in various painting manuscripts. Therefore, the process of color printing and reproduction uses the phenomenon of heterochromatic spectrum to achieve the purpose of color reproduction.

 

Isochromatic spectrum is conditional, must be under the same observation conditions, mainly the same light source. The experiment shows that two homochromatic spectra, because of the change of lighting source, no longer maintain the same color. In most cases, it is difficult to achieve accurate isochromatic matching, and generally only approximate isochromatic matching can be achieved. In color printing, there will be a certain color difference when the primary color ink is used to adjust the special color ink or use the primary color dot to copy various colors. In actual production, there should be color difference between the copy and the original manuscript when matching the chromatic spectrum, but the replicator should try to control the color difference within the allowable range stipulated by the standard.