Ain’t technology grand? Digital printing has certainly changed things. Few of our customers today know what rubylith is (or was), have ever seen a stat camera, or have come home at the end of the day with a few miscellaneous words stuck to their elbow like oversized flakes of dandruff.
But digital printing is a two-edged sword and it takes some special considerations to get the most out of it. Let’s begin with the most obvious one, color. At a traditional printer (ink on paper), each color you add will probably change the price of your job. At most digital printers (toner-based), there’s one price for color and one for black and white. At a traditional printer you may pay a bit more for a piece printed, say, all in blue. It will probably include the expense of a press wash, but it will still be a one-color project. At a digital printer, you will probably be charged the same price as if you were printing a full color photograph covering that page.
These are considerations that should probably be made at the the design level. Once you’ve designed the piece in one color, you’ve substantially diminished the likelihood of digital printing as an economical choice down the line. On the other hand, if you plan on using digital output, let your creative juices fly and take advantage of the power of color to make your point or sell your product. Don’t forget to add color photos wherever you can. This is an expensive process in traditional printing; you need scanning, 4-color separations, and careful alignment of the plates for it to work. Not so in digital printing; take the electronic file of the image and drop it in the layout. Done. Well, you might want to make sure the image is CMYK and not RGB.
Which brings me to difference between the color models. If you’ve ever gotten your digital prints back and noticed that the color photos looked a bit flat or off color, there’s a chance you may have used RGB files instrad of CMYK. Most digital cameras, by default, shoot in RGB. This is the Red-Green-Blue color model. Almost all the light that is emitted by natural sources (e.g the Sun) is in this color spectrum, as most probably is the monitor you are viewing this page. It is the spectrum of transmitted light. If you think way, way back to High School health class, you may vaguely remember something about “rods” and “cones.” Well, that’s the connection, we see by interpreting the RGB spectrum. If you do the math you find there’s nearly 17,000,000 colors you can make with this combination (there are 256 steps of each color that are possible on your RGB monitor). Turn on the red, green and blue lights full strength on you monitor (or in the Sun) and you have white.
CMYK (Cyan, Magenta, Yellow, and Black) on the other hand, is what we see when most things are printed. It is a product of reflected light. Actually there are only three colors involved: Cyan, Magenta, and Yellow. Black is added because we live in an imperfect world. In theory, if you mix 100% Cyan, 100% Magenta and 100% Yellow, you should get Black. But you actually get a muddy reddish brown. Black is added both to achieve a real black and to replace some of the other colors in a process called Under Color Removal (UCR) or Grey Component Reduction (GCR). Maybe more about that at a later time. The CMYK spectrum only gets us about a million colors (100 steps of each of the three).
How and where an image is converted from RGB to CMYK is critical to how it will look when it’s printed. As you can see, the gamut (or range of colors) in RGB is substantially greater than that of CMYK. And since 100% of all the colors in one model equals white and in the other it equals black, you might guess there is more to converting between the two than meets the eye. The best plan is to convert the color in software designed for that purpose: PhotoShop. While most RIPs will do this conversion on the fly, some handle it much better than others. Making the conversion yourself in PhotoShop will at least let you know which colors, if any, will change.