The key to avoiding problems is consistency. Always use the same application settings to maintain a stable environment. The importance of quality control should not be underestimated, as without it, you cannot have color management. And without color management, your remote proofs do not bring you the time and cost savings you seek.

The fate of a product can sometimes rest on the packaging alone. Therefore, anything that can be done to improve the quality of product packaging is welcomed by the package printer’s clients, who also want their projects faster, better and cheaper. Package printers, in turn, are always looking for ways to maximize their potential. Vendors are meeting this need with new technologies that can help bring the quality of print to a higher level and make package printers more productive at the same time.

Drop-on-demand, piezo digital proofing is one such technology. It is becoming an industry standard for quality at an attractive price per proof, saving flexo shops added time and money when it comes to proofing projects. These devices offer color consistency as an affordable alternative to other higher-priced proofing systems.

Most proofing systems are designed for commercial printing. Requirements for commercial printing vary greatly from package printing. A good proofing system for packaging print jobs must be able to handle the specific needs of this unique production environment.

Proofing priorities for package printers include matching special logo colors; simulation for uncoated and coated card and corrugated board; and possibly matching the behavior of both an offset and flexographic press. New proofing systems supporting dot simulation from 30 lpi (for corrugated board) to 175 lpi (for labels, flexible packaging, etc.) are beginning to be offered by many vendors.

One way package printers can save time and money without sacrificing quality is through remote proofing, which can be done at any location and is both high in quality and affordable. Instead of having to rely on ground transportation to physically bring a proof to another location and wait for the sign-off, a simple digital file can be sent electronically, for example, to an inkjet proofer at the client’s location. The proof is checked, and the waiting is over – you can move ahead on the project.

In order to trust the proof that is made on the other end, you need to make sure that it is consistent with the image you send and with the proofer that is going to be used to print it. Even the monitors used to look at the image need to be calibrated accurately so that everyone is viewing the same color gamut of the same image. Remote inkjet proofing is a great leap in that direction.

Color Management & Proofing
To ensure consistency of images successfully, color management must be employed to ensure that all colors throughout the workflow are consistent and accurate. Prior to 1993, color management was a proprietary function, and it wasn’t very useful when dealing with devices that needed to be linked together. Color characteristics could be defined, but not communicated.

Then in 1993, several vendors founded the International Color Consortium (ICC). This moved the graphic arts industry from a closed system to an open system, allowing graphic arts professionals to mix and match the best possible equipment from different manufacturers. This also paved the way for creating color standards, known as the ICC profile.

Producing a color-accurate proof is one matter; producing a proof that can predict how a press will print—which requires a workflow-integrated color management system (CMS)—is another. The CMS lets you create color profiles, which characterize specific devices so that one can mimic the other. Unless all the devices behave consistently, however, the results will vary. For example, the tonal behavior of a proofer can vary for a number of reasons. Over the course of time, even when the same color profile for the same proofer is used, the color may shift in the proof printed. A quality management system will prevent this from happening by allowing you to verify color consistency and determine when devices need to be recalibrated, thus creating a stable environment.

Verifying device behavior at all remote sites and recalibration is especially important for remote proofing. Unless the system at the remote location is calibrated to the same standard as the one at the primary site, it is impossible to reproduce matching proofs. Software can solve this by allowing control strips at both locations to be proofed and measured. Any deviations between the two devices are determined and corrected.

Therefore, the CMS becomes important as flexo shops move into a digital environment. The CMS helps to control the exchange and reproduction of images across a wide range of devices. While the color behavior of each device is different, the CMS links these disparate devices together while keeping the color under control.
Every color device in the workflow—from scanner to printing press—records, displays or outputs color differently. That’s because each device sees color using a different color space or gamut. Scanners and monitors record and display color in RGB. Proofers and presses print in CMYK or CcMmYK (six-color proofers add a light magenta and cyan to the four colors).

The CIE (Commission Internationale de l’Eclairage, a standards organization formed in 1931) model represents all the colors that can be perceived by the human eye. The CIE Yxy model is two-dimensional. The CIE LAB model is three-dimensional. The industry-standard IT8 reference target is used for both printing and profiling. For example, you print an IT8 target on the printing press device and from the proofing system. You then use a measurement tool known as a colorimeter or spectrophotometer to measure the color values of the output. The CMS reads the LAB values then links these CMYK values to the measured LAB values based upon the created output profile and proofer profile. Spot colors are also reproduced in the same manner. The solid values of the spot color can be measured in a LAB color space and are then converted into CMYK or CcMmYK values during the RIPing process.

Color Profiles
Color profiles are the DNA of input and output devices. They provide mathematical detail about the device’s color space and describe its unique characteristics. The CMS takes that information and remaps it to replicate the DNA of another device.

For example, the CMS reads the color profile of a proofing device and one of a printing press. It learns that the color gamut of this inkjet proofing system is much larger than that of the printing press. It might also see that this particular proofer reproduces very warm blues. It will take the coordinates of the proofer’s color space and remap them to match those of the printing press. At the same time, it will compensate for the blue characteristic of the proofer. As a result, the proofer will be able to match the color output of the press.

The CMS also helps to reduce waste and increase productivity by optimizing automation. For example, without color management, to reproduce an image during scanning, proofing and printing steps would require trial-and-error testing – wasting valuable materials and time.

With the CMS in place, functions such as calibration are easily performed. Calibration makes sure the monitors with which images are viewed and the proofers that print those images look the same, day after day after day. With each of your monitors and proofers thoroughly measured and checked, your production workflow runs more smoothly. CMS software then runs through additional calculations, resulting in a color gamut for your devices. This gamut represents the maximum range of colors each device can reproduce.

Managing the variety of color gamuts within the operation becomes the challenge. Automated workflow takes care of it, resulting in top-quality flexo imagery.

Substrates and Color
Every flexo printer and trade house wants the final job to be simulated as closely as possible during the proofing process. Therefore, it is necessary to not only render the correct subject color based on a proofer profile, but also to render a background color onto a given substrate to mimic or simulate the color of the substrate actually printed. This is commonly expected when the variety of substrates is broad in any packaging environment ranging from corrugated to folding carton, label or flexible white film. This is referred to as the creation of an absolute rendering profile, where a spectrophotometer reading is taken of the background color of the printing substrate. This color is then applied during the proofing process to render that of the substrate, whether it is yellowish or brown, or a white board that has a gray cast.

Special substrates for creating dieline proofs, such as clear film or dimensionally stable white overlays, are becoming more widely used as a substitute for silver halide-based dieline proofs. This low-cost, for-position-only (FPO) proof using ink-jet technology allows printers and trade houses to utilize overlay proofs for indication of folding, trim, die cutting and die station positions to assist in the plate mounting process.

Other materials, such as adhesive-based vinyl materials, enable color proofs to be generated on an ink-jet proofer. The proofs can then be applied to the printing substrate for the creation of a mock-up, which is fast becoming an industry standard service as packaging trade houses broaden their services offered to the client. Package printers rely on the accuracy of digital proofs to create the mock-ups for test marketing purposes.

Consistency: Key to Success
Maintaining a stable color environment is essential to successful color management and predictable color. Each of your color devices, therefore, must be calibrated using a consistent standard or target. In other words, you need to ask each device the same question and get the same answer.

Quality control should encompass all the variables that can affect color. The color settings of application software also influence color perception. Image-manipulation programs, such as PhotoShop, come with their own color-management settings. You can choose to work with system settings or with the application settings. The color will be different from one to the other.

The key to avoiding problems is consistency. Always use the same application settings to maintain a stable environment. The importance of quality control should not be underestimated, as without it, you cannot have color management. And without color management, your remote proofs do not bring you the time and cost savings you seek.

[时间：2003-09-15  作者：Bisenet  来源：Bisenet]