Good, Better & Best Approaches to Achieving Color Accuracy

“Good” Benefits

Here are the benefits:

• Spectrophotometers can store thousands of reference colors (including Pantone libraries) inside the instrument and color differences (Delta Es) between a printed sample and a reference or brand color can be automatically displayed
• Spectrophotometers can recommend precise density adjustments to achieve the lowest Delta E on press for a particular color. This is a valuable feature that can dramatically reduce pressroom makeready times because the operator is shown the precise density value that is required for each color in the job to achieve the lowest Delta E. In some cases, this may indicate that an anilox roll must be changed and, in other cases, it may indicate ink problems that cannot be fully overcome with density adjustments alone. In either case, this is valuable information for the operator and can save considerable time and materials. Consider the example in Figure 1 where the instrument is indicating a 0.18 density increase that will greatly reduce the current Delta E of 10.2 down to a Delta E of only 0.9 for this match to Pantone 647 C
• Spectrophotometers typically have a graphical display of color differences indicating if the printed sample is too red, too blue, too yellow, etc., which can be very helpful if the operator decides to modify or “tone” the ink on press
• G7 and ISO reference print conditions are stored within most press-side spectrophotometers which can provide pass/fail indication according to these references and recommended changes to comply with these standards
• The calculation of ink opacity is included and invaluable when printing white ink on clear substrates where accurate process and spot color matches are required
• While still relatively new, SCTV, otherwise known as Spot Color Tone Value (ISO 20654:2017), is a new formula that spectrophotometers can use to calculate the tone value (TV) or dot percentage of any spot color ink based on color measurements, instead of CMYK density values. The end results are more accurate TV or TVI measurements that allow for more visually linear tone curves for spot colors with vastly improved predictability on press

Better: Adding Press-Side Color Quality Software

Building upon the upgrade from densitometers to spectrophotometers, the addition of press-side color quality software offers enormous advantages by connecting different departments, users and print locations for easier communication, visibility, reporting, traceability and accountability regarding color quality.

These software solutions are typically network or cloud-based utilizing SQL databases and are highly scalable to accommodate the needs of small and large production environments. With software installed on computers in the ink, prepress, production and quality departments, the communication of color standards, job information and tolerances has never been easier. In addition, because color measurements from printed samples are saved to the database, these software solutions offer sophisticated reporting tools.

Typically, prepress will create “jobs” that contain the aim CIE Lab color values for each color in the artwork, along with critical print metrics (density, TVI curves, etc.) and associated tolerances. The job is then saved in the software’s database until it is running on press. Once on press, the operator opens the job and has all the aim values and tolerances loaded onto the computer screen.

At this point, during makeready, the operator uses a handheld spectrophotometer to measure the required color patches indicated in the software and is immediately shown pass/fail indicators for the print metrics in the job, along with recommendations on how to improve the color match. Beyond makeready, operators typically continue to measure printed samples throughout the pressrun (usually at the end of each roll) to ensure color accuracy and consistency throughout the job.

“Better” Benefits

Again, there are some key benefits of note:

• Color quality solutions have the ability to directly control press-side spectrophotometers, which includes automatically configuring the instrument measurement settings and ensuring the instrument calibration is performed at the recommended intervals to ensure accurate color measurements. Together, this lowers the prerequisite skill level and spectrophotometer knowledge required by the press operators
• Once a job is opened in the color quality software, all color standards, print metrics, and tolerances are easily and precisely communicated to the press operator and loaded into the software. This ensures everyone is targeting the same aim color values and print metrics across shifts, locations and future re-runs of the job
• Large, easy-to-understand graphics present pass/fail indications according to tolerances set up in the job for color and print metrics (CIE Lab, Delta E, density, TVI, G7, etc.)
• Corrective actions are also displayed to help operators make the most efficient changes and quickly get within the job tolerances
• This information reduces the barrier of entry for newer, younger press operators and helps to ensure color accuracy and consistency across different press operators

Score card systems are typically included in color quality solutions and allow individual print metrics to be weighted, scored, and rolled up into a single pass/fail number that can be used to more easily assess the color quality of the job.

• When the job is complete, every color measurement is saved back to the job, so the quality department can prepare job reports for either internal stakeholders or the brand customer demonstrating adherence to the job color specifications
• Many color quality solutions also include powerful query and data analysis tools, which can leverage the mass quantities of job and color data being captured and saved into the database
• These tools deliver actionable insights to help ensure more accurate and repeatable color results with continued savings through reduced makeready times, less waste and fewer job re-dos