The Sign Connection: The Four Cs of Color Management

Many articles have been written about the benefits of color management—better color; more consistency; “easier” color workflow, and so on. But what are the basic requirements for a color-managed workflow? This article will discuss the basic four requirements of a color-managed system: the Four Cs of Color Management. All four items build on each other like a house of cards; without satisfying the first requirement the second is difficult, and so on.

 

Consistent Color

Before anything else, a proper color workflow requires consistency in every piece of the chain. A stable monitor is a must, and of course the color output from the printer must also be consistent. While modern printers are capable of consistent output, there are some factors that can affect consistency. Stable environmental conditions are a necessity if consistent color is your goal. Where is your printer located? Is it by the “smoking door” or the rollup door in the back? What about the thermostat—do you turn the A/C or heat off at night and then flip it back on in the morning? Wide swings in both temperature and humidity can have a huge impact on the absorbency of the media, which in turn can radically affect the quality of the color output. Relocating or otherwise shielding the printer from exterior doors can help consistency. Use of a programmable thermostat allows the facility to warm or cool to a stable temperature and humidity in time to start printing at the beginning of the day.

 

Printer Calibration Considerations

The next step is calibration. By definition, calibration is the act of returning a device to a known state. For example, before weighing something on a scale we check to ensure the scale reads zero when empty—we’re calibrating it. In the world of color, calibration takes two main forms. The first is monitor calibration. As many of us know, what is seen on the monitor doesn’t necessarily match what is printed. But with calibration it can come very close. And by calibrating the monitor we also eliminate the “drifting” of color that can occur over time. Monitor calibration is fairly simple, but it does require the use of instrumentation such as the X-Rite EyeOne Pro or EyeOne Display. These devices attach to the face of the monitor and actually read the color characteristics. From these readings software automatically adjusts the color output to ensure proper color display on-screen.

Monitor calibration is a nice touch, but the most important device to calibrate is the printer itself. Using instrumentation like the X-Rite EyeOne Pro together with modern RIP software, we can generate a calibration chart consisting of steps of discrete ink colors—five, 10, 15 percent cyan; five, 10, 15 percent magenta, etcetera. The chart is printed (and cured, if necessary) and then read back into the RIP using the calibration device. From there the software compares the tint of ink in the file to the actual amount of ink printed, and seamlessly makes an adjustment to the RIP software to ensure that when we expect 25 percent cyan, we actually get 25 percent cyan when printing. While it may sound a little scary, the machine takes care of the majority of the work and the process mostly involves printing and then scanning the image—no color expertise is required. The process should take 15 minutes or less on a solvent printer, and under five minutes on an instant-curing printer like a UV-curable or latex printer.

There are a couple of items to consider with respect to printer calibration. First of all, changing the media, ink, resolution, or dot pattern will change the calibration. This means that if I’ve calibrated my machine for 720 DPI printing and then run a job at 360 DPI, it will not use the 720 DPI calibration. If you typically use more than one resolution, you’ll have to calibrate each mode individually. The obvious other question is, “how often do I have to do this?” To ensure the best possible color, I recommend recalibrating under three circumstances:

  1. Every time you open a fresh roll of media. Even with the same lot, media can vary and so the color will vary as well. Recalibrating is a quick, painless way to account for that variance.
  2. Every time that reprints are a possibility. This includes printing a portion of a large job with the remainder to be printed on another day, or even printing a vehicle wrap where a panel may be damaged during installation a week later and needs a reprint. Returning the printer to a known state each and every time helps ensure that the color matches between what was printed last week and today.
  3. When the customer is picky over color. If you’ve just calibrated the printer this morning, you probably don’t need to recalibrate it this afternoon to make your customer happy. But in most other cases, it’s cheap insurance that the customer’s color expectations will be managed properly.

 

Time to Profile

We have consistency. We have calibration. The next piece of the color management puzzle is characterization. In terms most are familiar with, characterization is the process of creating the “profiles” used to print on media. These profiles consist of mechanical settings such as heater and stepping information; information about how much ink the media can hold at a given print speed; and an ICC profile—a “recipe book” describing the color characteristics of the printer-media combination and what inks are required for ever possible color. How to create such a profile is beyond the scope of this article, but there’s an important message that needs to be heard: each and every media you print on your machine should have its own media profile. If you’re printing on Media A, you can’t use the Media B profile and expect great results. On a weekly basis I see someone on a message board exclaim that he “uses the 3M ControlTac setting for everything” he prints—and then it’s followed by “but.” But he can’t get good neutral greys without forcing black ink only. But burgundy comes out brown. But blue prints purple. But the media is too saturated with ink to use the takeup roll. These are all inherent problems with using the wrong media profile. Use the right media profile and recalibrate for your machine and specific roll of media, and you’ll be fine. If you can’t find a profile for the media, then your choices are to make your own or be satisfied with whatever results you get from using another profile. There’s no holy grail of color management—there’s no one profile that works perfectly for everything.

 

Color Conversion

The last C of color management is conversion. Conversion is the process of analyzing the colors of a design file and transforming those colors into the specific ink percentages on your printer-media combination to get the best results. There is an inherent difference between the exact color formula used in designing a file and the ink percentages required to duplicate that color on a printer. Even if you design in CMYK, you’re designing using ink colors from an offset litho press. Your printer’s ink colors are very different, and the RIP needs to convert the design file’s colors so that they look like what is expected. This is why, for example, a file designed with 100 percent yellow only may result in the addition of magenta or cyan dots in the finished output. The RIP is interpreting 100 percent offset litho yellow, and converting it into the formula required to match that color on the printer which may result in something other than pure yellow ink. With lower-resolution printers this can be a problem, and there are strategies to address it, but in general this is a good thing—it’s proof that color management is taking place. Conversion is completely transparent to us. It requires no direct interaction other than making sure that the RIP is set up properly and the proper calibration and media profiles are being used.

There is no magic “make my color perfect” button. Establishing a color-managed workflow takes hard work, some understanding of the process, and even specialized equipment. But the end result is worth it. Rework should be significantly reduced, and turnaround time on difficult color jobs can easily be a fraction of the time taken in an unmanaged environment. But the most important effect by far is that the increased confidence in your entire color system allows you to go sell color work you may have otherwise shied away from.

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