The role of paper in the G7 process

The printing process contains many important variables. Paper is one of them. In order to help printers to standardize the printing process, international organizations such as GRACoL, SWOP and SNAP have introduced specific operating procedures. Although paper is also included in these procedures, it did not become a G7 until IDEAlliance developed it. An integral part of the color measurement process. At present, the G7 is rapidly accepted by the printing industry. It has also become an important tool for color correction and replication in today's world of multi-purpose output.

The G7 defines a color correction method for offset presses, proofing systems or other CMYK imaging devices. This mode is not perfect, but it is very useful in the printing process.

The core of G7 method is to use visual appearance method, control the reproduction of gray and measure the density and chroma value of neutral gray to realize the exact matching of the visual effect between the proof and the print. It is an ideal solution for achieving a consistent visual appearance across different devices.

Steve Upton, Chromix's color expert, said: "Matching colors is like setting up a tent. You just have to deal with the pillars of your tent - that is, the balance of the grays. The rest is much simpler. ”

The G7 just provided us with a method. The printing company also needed to establish its own target color space. They can choose between many existing standard color spaces, or they can create their own color space. For example, GRACoL 1 for sheetfed printing and SWOP 3 or SWOP 5 for publication printing are quite The color space is welcomed by the American printing factory. In addition, Fogra can also identify multiple color spaces.

Paper can change the color effect
G7's gray balance formula is related to the substrate, which automatically adapts to the color of the substrate. Therefore, choosing the right paper and density and matching colors with the G7 process is crucial to producing predictable prints.

However, please note the change of paper. If the paper you choose is different from the one used during the calibration process, the color effect of the entire print will change dramatically.

The role played by paper in the reproduction of high-light shades, mid-tones, and saturated shades is very important, but its influence on different shades is also different.

Paper variables include shading, absorbency, smoothness, and opacity, and any change in one of these attributes will cause a completely different product to be output by a printer or printer calibrated by the G7 method. Even the same plate (or file) may have completely different results.

The G7 usually uses an empirical formula to make adjustments to changes in the paper—adjustments to the highlights are larger and adjustments to the shadows are smaller. The other attributes of the paper are not easily adjusted. The relationship between print density and dot gain does not have much to do with the type of paper.

In theory, paper using optical brighteners is less likely to be matched by output technology by means of printing techniques unless people use the same paper for each printing process. Most color management experts have recommended that people use inkjet printers and other proofing equipment for proofing on production paper.

When we use the G7 method to control printing, we must insist on tracking the paper. Remember that once the paper changes, you may have to adjust the entire production system.