Consistent On-Brand Color Management for Packages

Best practices for color consistency amid tightening brand tolerances.


As brand companies strive for ideas that provide faster-to-market strategies for packaging, and more customization to reach an ever-changing demographic, the demand to utilize different printing devices is a requirement. But it is critical to know that any new print technology is capable of matching existing print technologies to ensure packaging on the shelves matches, no matter what print technology manufactured it.

If packages from the same brand do not match one another, the consumer naturally questions if the contents of the packages match, or if they are different products, out of date, or counterfeit. A different outside package causes the consumer to lose confidence that the consistency of the actual product is good.

Two key attributes are required to ensure that the consumer doesn’t lose this confidence. First, the brand has to establish what its product should look like for the given package. Think of this as the golden master original that all future renditions should match (defined as CxF-X4 file), and as the established bullseye for the reference image.

Secondly, the brand has to establish how much variation it is willing to accept from the bullseye (how many rings away from the bullseye is acceptable) based on a type of delta E (a method to quantify color difference, with the bigger the number showing a bigger difference). It is important to note that no print device will have less than 2 E-Factor variation as of this writing.

Though a very simple concept, many companies have not been able to implement this scenario. Many brand companies have developed a complicated scorecard type of system which gives points for each process control metric that is met to a given tolerance (i.e., if cyan 100% patch is within 3 delta E, get 5 points; if within 5 delta E, get 3 points, etc.). In the end, a print that scores 85 or greater is supposed to be acceptable, but compared to what? Professionals using this type of system experience a couple of huge limitations: First, just because a print scores greater than a given number, doesn’t mean it will meet that brand’s expectations of a color match. Secondly, the score card doesn’t define the color variation between prints: two prints that have the same score often don’t look anything like one another, and they have an unacceptable match to one another, never mind to customer expectations. The E-Factor metric overcomes both of these limitations.

Most packaging consists of both process, and brand/spot colors. Tolerances need to be defined for both process and brand color.

When developing tolerances for spot/brand colors, the industry standard is to use a metric called delta E (ΔE2000), in which the lower the number, the closer the match. There are different delta E formulas that produce different results, and even the industry-accepted delta E 2000 formula has inherent limitations because the color space is not linear, and with some colors, the same delta E in different directions will result in inconsistent values such as the gold color shown in Figure 1.

Sometimes, it may be necessary to provide a higher delta E tolerance for some colors that are hard or impossible for CMYK printing devices to match (bright, light colors in particular). It is important to ensure that the color reference is capable of being rendered in the desired CMYK color space, and if not, a higher tolerance needs to be granted to that color to accommodate for the gamut limitation on the output device.
 
Brand colors are typically assigned to line art or text, and it is appropriate to set a tolerance on delta E, but what about the thousands of other colors on a page? This is where a new
metric, E-Factor — based on a type of delta E — works for defining tolerances for page appearance consisting of thousands of colors and/or images. There are two parts: First, the brand assesses color differences between multiple images (either online or with print samples), and by evaluating image comparisons with different levels of color difference, they decide what level of color difference is acceptable to meet their expectations, which is called their E-Factor (Expectation Factor).

Secondly, the print process is measured to quantify if it can meet customer expectations. Measuring color bars off the printer allows the system to define the E-Factor to both the reference (accuracy), but also to itself over time (consistency). The same metric can be used for reproduction systems like printers, therefore, it is possible to quantify how a printing device reproduces the color against the reference. No reproduction
system, monitors, or printing devices are perfect, which means the E-Factor equals 0. Every device has some variation, and it is important to quantify the E-Factor.

If the print process E-Factor is equal to or less than the customer’s E-Factor, then the color match will meet the customer’s expectations. If the printer’s E-Factor is greater, then the printer will not meet expectations. E-Factor provides one number, which clearly communicates both accuracy to reference, and consistency over time. 

It is important to understand that different printing processes have different levels of variation based on a multitude of factors, and this E-Factor methodology allows anyone to quantify any print process to ensure that it will meet the customer’s expectations at any time.

Once the brand defines its expectations of color match with E-Factor, it will communicate this expectation to its suppliers as part of its “Print Requirements” so that its supply chain understands the brand’s required level of color match and consistency. In return, the printer will be able to provide “Print Quality” data that shows the brand that the printer was able to perform to meet the brand’s expectations.

Print variation is typically dependent on multiple machine factors, including:
1) The printing device is in sound mechanical shape,
2) Continuous maintenance is performed,
3) Raw materials (ink, paper) are consistent.
4) The operator runs the equipment in a consistent manner, and
5) The operating temperatures are within the print machine’s parameters

Print variation occurs on multiple levels, and management needs to know how to report this variation to ensure the brand’s expectations are met. The first level of variation happens within the imaging area (within page variation). This defines the color variation within the given area. The second level of variation relates to between-page variation (within a job or repeatability).

The third level of variation relates to between-job variation (reproducibility), which can be
related to different presses, operators, locations, and timing.

Printers need to be sure they have variation under control before they attempt to improve color accuracy. Color accuracy relates to how close printers are matching the bullseye, which represents the target reference of the product. Both variation and accuracy can be measured using E-Factor, and it is equally relevant in both cases. If the desired E-Factor is 4, the print variation is 3, and the accuracy to target is 3, expectations will be met. If either variation or accuracy is more than 4, the expectations will not be met.

Print accuracy is typically dependent on the prepress handling of the files and applying the correct G7 tone curve, or International Color Consortium (ICC) profile, at time of printing. This part of the puzzle is not applied by the press operator, but by the prepress side of the organization. It is important to understand that most often, G7 curves are applied to a conventional press workflow (offset, flexography, web, screen), and ICC profiles are generally applied to a digital (inkjet, toner, etc.) press workflow. G7 tone curves relate to four one-dimensional curves that affect tonality and gray balance of the print to provide a “shared” print appearance.

Notice that the term “color match” is not used. G7 curves versus no curves will improve color match, but it does not, and cannot, ensure a color match due to the inherent differences between different inks and toners. (A G7 curve does not affect the color of any solid primary or secondary ink.) ICC profiles take more work to create and apply, but they provide a more accurate result because they perform a four-dimensional transformation on the file and can affect all tints and all solids in order to perform a color match between printing devices. When customers are demanding an E-Factor match in the 3-4 range, it is much preferred to use ICC profiles to convert the color for the output devices to match the target reference conditions communicated by the print buyer.

Instrument and Lighting Factors

When dealing with the supply chain, the ramifications of using different color measurement instruments come into play. In any manufacturing industry*, there is an Instrument Gauge Factor (IGF), which is used to compensate for the difference between different instruments. In the same way that two scales will display different weights, even when stepping from one to the other, different measurement devices measure color differently, and will compound the differences from the source. By using an IGF and assessing instruments’ consistency based on E-Factor, it can be determined if certain instruments are not precise enough to be used in the given workflow. In addition, instruments can be harmonized to the brand company’s master instrument to help greatly reduce between-instrument errors, providing more tolerance for the print to meet the customer’s desired E-Factor.

In addition to the variation of different measurement instruments, different lighting can play havoc through the supply chain if not strictly measured and quantified on a regular time frame. Each lighting system can vary dramatically from one another, and until now, it has been difficult to quantify and apply the results to a workflow. Now, E-Factor can be used to assess how consistent lighting areas are, and how differently they render color to one another. If the lighting exceeds the customer E-Factor, then lighting has to be corrected to ensure the resultant color is not improperly illuminated, which will cause a mismatch when none exists.

Calculating the lighting’s E-Factor can eliminate many false causes for color mismatches. Two ISO-compliant light booths can visually render the same print to be 3+ E-Factor different from one another. This means the same print, viewed under two ISO-compliant light booths showing a 3 E-Factor difference, which is outside of some customers’ expectations. Everything about the print was correct, but because the light booths illuminated the prints differently, the eye perceived an unacceptable match. Remember, without light, it is not possible to see color. The color of the light booth is critical for the print to look correct. There have been numerous cases where a customer failed a job due to improper lighting. In the past, it was very difficult to document the accuracy of light booths, but now, with affordable measurement devices and software, it is easy to document their accuracy to the ISO reference, and document the consistency of light booths to themselves over time. Most importantly, it is easy to document the differences of light booths to one another.

Manufacturing salable color is not easy, but it is very doable with proper color management and routine process control scheduled by a color conformance system. This type of system provides notifications for all operators in the supply chain to remind them when it’s time to check the printer/light source/measurement instrument to ensure it is operating within E-Factor tolerances. If it isn’t, the system will immediately warn the operator that the component needs to be fixed to get it back into a salable condition. This Operator E-Factor report, created immediately when each print is measured, communicates to the operator of the printing device whether the job they are printing is salable or waste. This immediately improves profitability and productivity because the operator knows by the E-Factor number if they can run production, or fix the problem and then run once E-Factor is within tolerance. One E-Factor for all operators on all printing devices, anywhere in the world, which eliminates subjectivity and holds all operators accountable to the same level of quality. It is critical to understand that the tighter the E-Factor, the more money, time and waste will be required to achieve it.

From a profitability standpoint, it is important to choose an E-Factor tolerance that your customers are expecting today. If you choose too loose of an E-Factor, you will lose customers because their expectations will not be met, but if you choose too tight of an E-Factor, you will lose money. Profitability is critical to every print organization today, and E-Factor can standardize manufacturing and help reduce waste by reporting the status of every job to ensure the product meets customer expectations. 

* Suppliers for Boeing that construct parts of an airplane in different locations have to adhere to strict IGF numbers to compensate for the fact that no two
measurement devices of any kind render identical results. IGF allows variation in the process to ensure that the parts will fit together at the end. In the same
way, IGF allows color to match in the end, even when different measurement devices are used.

David Hunter
David Hunter is co-founder and principal at ChromaChecker. He is an accomplished and recognized expert in color control and management with a 30-plus year career in the graphic arts industry. As one of Apple Computers’ first three ColorSync Profilers, he co-founded the Color Conference with PIA, and was one of the first G7 Experts (still among six trainers in the world today). Hunter has co-authored several TAGA papers related to color matching and common color appearance, researching how buyers judge color. He is one of five North American members of the international CIE Committee (TC 8-16) studying how humans perceive common color appearance. Hunter has pioneered the E-Factor process, quantifying a person’s expectation of color match acceptance, and carries it through the complete manufacturing workflow. He can be contacted 651.717.0590 or david@chromachecker.com.