Printing FAQ - continued
What is spot color, and why is it cheaper than four color?
Spot color is used in a different way than process color. A spot color is a specific color of ink, which is usually printed onto the paper in addition to black.
For example, an advertisement may have a red headline, and a black and white picture. This is known as ‘2-color', black and red in this example (Do not be confused by the expression ‘black and white' ...you do not pay for the white).
In the above example, you pay for one extra ‘fountain' of color (red). This is because an additional press unit is required to print the additional color. There is also the expense of the spot color ink, and a small bit of increased ‘start-up' waste as well.
Spot color is cheaper than four color process for several reasons. There is only one additional color, only one additional unit is used, and not as much start-up waste is generated.
What spot colors can I use? Can I get periwinkle?
Most printing companies have a selection of ‘house' or ‘standard' spot colors they keep in stock. Other colors can be mixed, or special ordered (expect an increased cost for non-standard colors).
There are problems trying to specify colors like periwinkle, kelly green, dark blue, etc. What exactly do you mean by dark blue? Should it match the ‘dark blue' crayon, or your ‘dark blue' suit? Clearly, something more accurate is called for.
There are several different schemes for identifying and specifying colors for printing. The Pantone Matching System is the most commonly used. A collection of PMS color samples (a ‘Pantone stick') will allow you to choose a suitable color. The color will have a number, such as PMS300. With this number, you can specify exactly the color you want, secure in the knowledge that everyone talking about PMS300 is referring to exactly the same color.
Can I use any PMS color? What about colors like ‘Reflex Blue'?
Not all printers offer all colors. It is common for a printer to limit ‘two digit poster colors', which are flourescent colors from the Pantone system, and metallics like gold and silver, for environmental reasons.
Some press equipment will not perform well with some colors. For example, colors with a high proportion of Transparent White (a mixing color) can cause problems when subjected to the UV lights of a UV-set press.
Pantone colors are formulated from mixing colors. It is possible to use most of these mixing colors like regular inks. Reflex Blue is a Pantone mixing color, and is commonly used as a spot color.
How good of a match will I get to a PMS color?
This depends on the nature of your project, for many reasons.
Imagine a PMS color printed into orange paper... of course, the orange paper is going to affect the color of the ink. While it is unlikely your project will be printed on orange paper, differences in paper stocks can affect appearance of the final color. And not just the color of the paper, but the finish, coating, brightness, and weight.
On a four color process page, spot colors are not usually printed as spot colors; they are converted to process color. Many Pantone colors cannot be accurately mixed from CMYK, especially oranges.
If, for example, you use the same spot color on every page, you could be in for an unexpected surprise when that color does not match on the process color pages. There are two ways to deal with this issue.
When picking your spot color, choose one that has a match in four color. There is a special Pantone Process guide that shows both a spot color sample, and that color mixed in process color. Choose one where both samples look the same. Note that becuase of the nature of process color, this will get you a closer match, not an exact match.
Alternatively, it is possible to print ‘four plus one', or ‘five color'. The pictures will print in CMYK process, as will any other mixed colors on the page. The spot color, however, will print as a regular spot color, and should match as well as the rest of the colors in the project. Note this will increase costs.
I am mixing process colors, and I don't care about matching Pantone colors. How can I tell what mixes result in what colors?
This is a larger problem than most realize. Computer monitors are not very accurate when it comes to simulating CMYK colors. They are especially bad at light tints of color, and do not reliably compensate for dot gain on press. The best tool for picking four color mixes is a previously printed sample of that color, so you know what it will look like on paper.
There is such a resource, the Agfa Postscript Process Color Guide. It is collection of colors, all mixed from CMYK. This book was available from Agfa's website, but appears to be out of print now.