Test area - Do you pay attention to the color draft environment (below)

The CIE International Lighting Standards Association has seen that different light sources have different degrees of color influence on objects, and thus specified the following standard illuminants and specified their spectral energy distribution. (See table 1 below)

However, the above standard illumination body can be realized by different light source combinations (simulated spectral energy distribution), but different substances have different stability, so CIE recommends a series of standard light sources (artificial light sources) to match the above standard illumination body. (See table 2 below)

ISO 3664 standard observations talk about so many sources of light and lighting data, then what is the best color rendering environment? In 1975, the ISO International Standard Certification Association has proposed "ISO 3664 Observe the Lighting Conditions of Color Perspective Films and Replicas" (new edition is ISO 3664:2000), which mentions the observation conditions in the printing and copying process. See the following four points:
1. The spectral energy distribution of the illumination source 2. The degree of illumination and uniformity of the light source 3. Observe the environmental conditions—
1) Observe the environment -
2) Lighting 4. The stability of the lighting environment In fact, ISO 3664:2000 has stricter requirements for lighting sources (see Table 3 below). It considers the new color imaging technology and proofing system advocated by today, and also the materials in different light sources. Next, the problem of generating metamerism is regulated, and the new standard is formulated in response to the effect of the effect of the UV polishing agent on the printed matter.

A. Illumination Another important factor is that it recommends two illumination standards, which are used in the following situations:
1. High illumination 2000I±500lux - used to evaluate and compare images, and strictly evaluate prints.
2. Low illumination 500I ± 25lux - used to resolve dark-detailed details of the image under similar final viewing conditions.
(Individuals believe that high illumination is suitable for use in various printing production processes, and when comparing the details of an image alone, low illumination can be selected.)
B. Observing the environment Observing the environment may be a neglected part of the printing industry. I believe we must have seen many things, posters, ink, cigarette packets, mobile phones, etc. around the observation environment of the workshop. The place is still next to the window sill, and some of it is covered with dust. There are the following tips in the ISO standard:
1. Minimize ambient disturbances.
2. After entering the observation environment, the judgement of the printed products should not begin immediately, so that the workers can adapt to the environment.
3. There should be no extra light entering the viewing area (including reflections).
4. There should be no strong colors around (workers' overalls).
5. The surrounding area of ​​the observation should be neutral gray and light, and the reflectance is less than 60%.
In fact, the above-mentioned issues are all that printers should pay attention to. These conditions are just a signal and they can be implemented. They can not only improve the environment for drafting, but also improve the quality of production and enhance the professional image of the factory.
The standard observation environment described in ISO 3664:2000 is widely spoken. The above is only rare. If manufacturers are interested in improving the observation environment, they can browse the ISO website and download the relevant documents of the standard for reference.
The easiest way to purchase a suitable light source device is to purchase a light box that conforms to the ISO standard. Of course, when it comes to a penny, a small one generally spends over 10,000 yuan, while a large one has a total of over 30,000 yuan. How can a printing company invest? However, this type of evaluation light box, in addition to meet the ISO requirements, there are many kinds of light sources can be selected, such as D65, D50, UV, TL84, A, etc., suitable for different industrial needs. Interested manufacturers can visit the Printed Materials Testing and Analysis Center in person. It is because of the relationship between the amount of investment that many manufacturers consider buying, but then find someone to customize. We can also request some suitable materials to match homemade light boxes.
1. Light tubes ─ ─ There are many brands of light tubes on the market that indicate a full 5000K (Unfortunately, CIE has not yet specified a standard light source for the D50 standard body), but it does not necessarily comply with ISO requirements. Therefore, we must pay attention to the following point:
1) Color temperature - 5000K
2) Color Rendering Index - ≧90Ra
3) Illumination - depending on the evaluation space (lux): lumens (lm) / square meter (m2) (Note: general light labels only indicate their lumens)

2. Panel material - as long as it can approach the ISO's limits such as:
1) Neutral chromaticity - the color index of the surface of the material can be measured with a spherical spectrophotometer, close to Lab -50,0,0
2) Reflectivity - Reflectivity measured with a gloss meter ≦ 60%
Test methods We usually measure changes in color temperature during production because the stability of the lighting body changes with time and environment. Although there are color temperature meters on the market (which can be purchased by professional photographic equipment companies), the price is not cheap, and there is a cheaper way to check the color temperature daily, like a sticker named GATF/RHEM (manufactured by GATF), When we put the instruction in the observation environment, when the color temperature changes, it will warn to remind the operator whether it is necessary to replace the light pipe. (See Figure 3, Figure 4)
Conclusion The complexity of the color printing process is well-known. The production of a printed matter can only be completed in a few steps. The company, the staff involved, etc., in different environments and at different times also have different evaluations of the printed matter. Therefore, we can only subject the printer to subjective evaluation by restricting the external factors of the environment. Only in this way can it be fair and objective to reduce disputes caused by the environment. So the standard lighting environment, light source is a must. I hope you can consciously improve and standardize your observation equipment.