The Key to Color Evaluation of Printed Reproduction

Color and density measurement is a common method to evaluate the quality of reproduction in printing. The best conditions for observing the replica during the printing process should be consistent with the final observation environment of the replica. If the final observation environment is well understood, the staff can monitor the quality of the replica under the same conditions, but this is generally unlikely. Therefore, in order to avoid the misunderstanding of color reproduction effect, it is necessary to use stable observation conditions in the process of product reproduction.

In order to ensure the use of uniform observation conditions in all replicas, it is imperative to recommend a unified observation standard. With regard to the conditions for observing color prints and photographs, the recommended standard is ISO 3664.

ISO 3664 includes the recommended standards for all requirements. At the same time, the standard also made recommendations for color screen image observation, as well as picture exhibition and appreciation of the conditions. This standard will also apply to the printing press and photography industry.

Standard of Light Source

In this standard, CIE D50 standard light source is recommended as the basic observation lighting source. Currently, when creating an image, color imaging and proofing systems use many new techniques: dye sublimation, heat transfer, ink jet, electrostatic imaging and so on. The use of these methods is gradually increasing the color contrast of the image, resulting in color matching variation.

The ISO 3664 standard retain the color rendering index and add two new standard parameters: the viewability and the UV chromotropic index. The two indices are derived from the CIE standard No.51, an assessment of the visual situation, an assessment of the spectral UV portion, in order to distinguish the actual light source from the cid50 ideal illumination more strictly. In other words, if the new standards are met, the observation equipment will provide more stable observation conditions. This will reduce some problem caused by the sensitivity of new materials or fluorescent lamps to paper and ink.

In the process of printing reproduction, there are several key factors to ensure stable and consistent observation conditions:

1 Spectral energy distribution of the illuminating light source

2 Light intensity and uniformity of light source

3 Environmental conditions (including observation environment and lighting environment)

4 Stability of lighting environment