Spot Color Builds
Shifting gears into spot color builds, it’s important to note that we are seeing increasing inquiries from customers to reduce the number of colors in designs. This request does vary slightly depending on the CPC. Much has to do with brand equity strategies, cost initiatives and speed-to-market desires.
Regardless of the underlying objectives, when these requests come forward, be pragmatic about realistic goals. Balance what’s obtainable with what could be detrimental to the brand presence and the ability for the printer to produce consistently. Deeper discussion must delve into ensuring proper execution and accuracy of spot colors that are identified as candidates for conversion to process.
By no fault of their own, designers are certainly limited when it comes to the tools to optimize spot color builds for process printing. It is even more complex, of course, when EG is added to the mix. What this means is when separators receive design files, more often than not the spot colors—whether intended to be printed as process or a line color—are indicated as solid coated, CMYK coated, color bridge coated or even RGB.
Sometimes, physical Pantone Bridge book values are used with the assumption that it will be a more accurate construction because after all, that is “ink on paper,” as opposed to an electronic reference. A commendable attempt but, as we will discuss, while those values may be good for SWOP or offset applications, they are often not great when applied to flexography, due to variability of ink sets (even when standardized), substrates and print conditions.
To demonstrate this opportunity, some specific example colors have been identified as “test subjects” in Figure 8: Rubine, PMS 109, PMS 155, PMS 185, PMS 2766, PMS 548, PMS 297, PMS 628, PMS 364, plus the cool gray set. These were chosen for their range from light to dark, pastel to saturated. They are colors actually used in some live prepress files. Sampling shows good examples of the complexity in this process requirement.
For starters, let’s take a look at the color builds on the test color set from Illustrator and the Pantone Bridge book. The charts in Figure 9 and Figure 10 show the color combinations for each build in both cases and the resulting Delta E when compared to an industry-standard profile, in this case CRPC7. For these evaluations, the cool grays have been left off the analysis but will be covered separately later in the article, based on some additional complexity and observations.
The first thing to note is that, based on the ICC utilized to generate the match comparison for this exercise, the Delta Es are not what we would consider “great.” While it’s clear a small number of these would most likely be sufficient, some of them are well above where the human eye starts to detect a difference. Additionally—and this is important based on our studies—many of the colors are built with four colors and in some cases have very small percentages in one of the separations. A best practice when looking at these dynamics is to consider critical aspects:
- First is defining the point in the low end of the tone scale that produces a high degree of consistency and repeatability. Extremely low values—for example, 1 percent or 2 percent—may not be as stable on press as something in the 3 percent, 4 percent or 5 percent range. As a rule, we often recommend 5 percent, even with some of the newest plate technologies, as it provides a solid foundation and in theory less variability. Having said that, this can be assessed with each printer and process, but the 5 percent value is used to demonstrate the color builds in this example
- Second is the number of colors in a given color build. Our research has shown that limiting the construction to three colors improves the match and provides a more stable print reproduction in the press environment. Again, this will be demonstrated as we examine the results of the conversion
With these points in mind, let’s take a look at what happens when we utilize the ICC profile to create the matches for the example colors instead of the generic values in the software or Bridge book.
Figure 11 shows the result in what we call the “pre-optimized” conversion. In this case, the colors are “thrown at the ICC” and spectrally converted in the software with no limits on highlight value or number of colors. As you can see, we have achieved a decent Delta E improvement, but many colors are using four colors, and some have values under the 5 percent limit.
Next, let’s look at what we call the “optimized” builds (Figure 12). In this case, we have applied the 5 percent highlight limit and restricted the conversion to 3-color builds. Notice, in most cases, the Delta Es are improved and the ones that did not improve or increase are still well within an acceptable range, proving the advantage of specifying the highlight limit and the number of colors allowed per build. Figure 13 shows the comparisons and resulting Delta Es.
The final examination of color builds is the cool gray color families that pose a different set of circumstances and require more attention. If the intent is to use a single cool gray color, the optimized builds produced may be sufficient; however, if the intent, which is often the case with these “family” color sets, is to use them in a vignette or shadow element, the builds need adjustment to avoid multiple colors in the separations.
Figure 14 shows the optimized cool grays, highlighting the builds in each. Note most are two colors, one is three colors and one is black only. This result is accurate when considering the ultimate match. A light-to-dark vignette would result in a 4-color build with color values added at step changes in the separation. That’s not ideal! It’s a significant issue on press and will not produce the desired results.
Figure 15 shows an example of the outcome if the family of colors is forced into a black-only build. It’s clear we have made a detrimental impact in the lighter colors related to the Delta E, but again, consider the goal of color consistency.
In this example, shadows, vignettes and other elements now can be produced seamlessly throughout the separation. If the Delta E is not acceptable from a design perspective, an evaluation of adding a second color (possibly yellow) could be made. For this purpose, it demonstrates the thought requirements that often need to be taken to ensure successful separations.
To recap once again:
- The process of standards alignment or print-specific ICC profiles is a critical step, based on the extensive utilization in color retouching and spot color build generation
- Your ability to understand the optimum separation strategy and apply it to the overall process not only supports color consistency—it enables it!
- Add these processes to overall print production, then couple them with sophisticated press-side measurement and analysis tools, and you have a clear recipe for success
Thompson presented this information as part of Virtual FORUM 2020 in the session titled Color Consistency: Achieving the Target. FTA members can watch every presentation from this session, as well as presentations from the other five Virtual FORUM 2020 technical sessions, on MemberConnect.
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