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: