Digital Printing - Color Matching

Color Spaces and Color Gamut:

For the most part there are two types of color space, device and independent:

A Device color space is the range of colors, known as the gamut, that device can display or produce. For example, our digital presses have a gamut of colors they are capable of printing using the process primary colors of Cyan, Magenta and Yellow. If a color is out of the gamut of the press, the closest match or substitution will occur.

An Independent color space is a predetermined gamut you can work in to create artwork. For example, sRGB is a color space created by HP & Microsoft to define a set of standard colors a PC computer monitor and personal printer can use for consistency. Adobe has also created an RGB space know as Adobe RGB. Examples of CMYK color spaces are US Web Coated SWOP and Uncoated. Below is an image, created by Jeff Schewe, of color spaces compared to the color range of the human eye. Colors within their respective outlines are attainable in those spaces.

CMYK vs. RGB

When designing, pay attention to the color mode you are using. If print is intended, using the correct set of primary colors will result in a more accurate printed piece. Computer monitors use RGB primary colors while presses use CMYK. In graphic design packages, you have the option of choosing the type of color mode you are using. In the screenshot below from Adobe Illustrator you see CMYK is selected for the new document.

Choosing a CMYK workspace will help the press accurately match colors. When you choose your color mode the software will use an Independent Color Space. For example, in Illustrator you can see the CMYK Profile is set to US Web Coated SWOP. If you had selected an RGB workspace above, the Color Space would be set to sRGB. Now whatever colors you choose will be within the Gamut of those Color Spaces.

Also, you will notice when you have selected a CMYK work space, the colors you define in your artwork are now made up of the four process colors of CMYK. Below is an example of creating a custom color in Adobe Illustrator. These CMYK values will be accurately assigned to the four colors in the press.

If you submit an RGB based file, a conversion must take place to CMYK for printing. Luckily, we have methods of accurately translating what you see on the screen with what is printed on the paper, as long as the colors translated are in the device's gamut.

How We Match Colors

Because digital presses use the four process colors; Cyan, Magenta, Yellow, and Black a simulation or mixing must occur in order to reproduce a color. Colors are created by varying the amount of these process colors and overlaying them on top of each other. To simplify the concept, think of choosing a custom color paint at a home improvement store and having them mix it for you.

The first two important tools in color matching are software and press hardware. The algorithms in the software communicate with the hardware to create the color and lay it down on the paper. The third part of the equation, and arguably the most important is the color specialist. This is the digital press operator who takes the time to alter that initial mix to create the intended colors (if necessary). This is done by varying the amount of CMYK used, reading the color profiles in the artwork, and determining the color space the original design was created in.

We try our best to meet our customers color expectations, but artwork designed on an RGB computer screen, may look different than what is printed on a CMYK press. Because of this we offer free proofs on color sensitive jobs. Digital Presses are excellent at producing repeatable results and proofing requires very little set up. Please call 212-566-5540 to discuss your artwork or submit it for a color review. We will take a look at the colors used and offer advice, help or graphic design services to set up colors for the most accurate print match.

Color Consistency and Delta-e (dE)

The last important piece in managing color is how consistent a color will stay throughout a print run. Once proofs are approved and the press begins a run, the operator will monitor the Delta-E (dE), or change in color, over the run. Digital presses also monitor themselves internally and adjust based on color and color density as the environment changes (i.e. temperature rises). At Quality Imaging, we try and maintain the lowest possible dE value over the run, and will even stop the press and manually tweak colors to keep consistency throughout.