As we all know, ISO 12647-7 is the international standard for digital proofing.
A digital proof that fully complies with ISO 12647-7 is actually not that simple. Not only does the well-known MediaWedge test color block meet the tolerance requirements, but also the brightness, phosphor content, abrasion resistance and light resistance of the substrate have corresponding requirements.
Soon after the release of the 2013 version of ISO12647-7, the requirement that the brightness value L is greater than or equal to 95 for the three types of general paper whiteness has become outdated. Although it is more suitable for Fogra 39, it is obviously not suitable for other proofing conditions, such as newsprint.
Therefore, the new ISO12647-7 standard abandons this requirement. It is considered that the proofing material is consistent with the printed material is the most ideal situation, but in reality this situation is often not met, so the following three requirements are proposed.
1. Glossy
First, the materials are divided into three types: matte, semi-matte, and bright. When the color matching between the proofing material and the printed material is required, it should be the same type of the three.
Therefore, it is not appropriate to use matte proofing paper as glossy paper for printing and color drafts, or to use light proofing paper as matte paper for printing and color drafts.
2. Paper Simulation
The color of proofing paper without pictures and texts should be allowed to simulate the color of printed paper (ie absolute contrast intention), and the color difference △E2000 should be less than or equal to 3.0. In order to ensure the accuracy of paper white simulation, the brightness value (L value) of proofing paper should obviously be higher than the brightness value (L value) of printing paper.
3. OBA
The fluorescent agent content grade of proofing paper should be of the same grade as that of printing paper.
According to ISO15397:2014, fluorescent agents are divided into four levels: trace, small, medium, and large. In fact, there are cases where there is no OBA (fluorescent brightener), so it is usually classified as five types. This is consistent with the classification in ISO12647-2:2013 and also reflects the principle of digital analog printing. Normally, we don’t need to make the control strip ourselves, but we need to know the target standard to be matched, and choose the control strips that are already available in the corresponding internationally renowned printing institutions, such as IDEAlliance ISO 12647-7 Control Wedge 2013, Ugra/Fogra Media Wedge CMYK V3
Although the digital proofing system is relatively stable, there will still be color shifts. The ISO12647-7 standard stipulates that CMYK field and 50% dots, and RGB need to be evaluated twice. The maximum color difference △E00 should not exceed 2.0. The same instrument should be used to measure the same position. If necessary, the proofing system needs to be recalibrated.
Standard digital proofing needs to simulate the printing color and visual appearance as much as possible, and there must be enough information to facilitate users. In the selection of consumables, instrument configuration, measurement mode, software settings, color calibration, and standard selection, attention must be paid to whether the requirements can be met, especially when converting to Fogra 51/52, GRACoL 2013 and other new standards. Pay attention to all aspects of the proofing system. Can meet the requirements of the new standard. Only with qualified and accurate proofing can we better guide printing production and maximize the effects of digital proofing.
