Converting spot color to process color in Illustrator or InDesign (You’re probably doing it wrong)
If you’ve been designing logos for brands or working in print design for more than the last 7 years or so, you likely felt the earth shake a bit in 2010 when Pantone introduced their Pantone Plus color matching system, which was developed to help printed PMS colors reproduce more accurately on computer displays. It was a move meant to better connect on-screen color with on-page color, but it came with unfortunate side effects to the average designer’s workflow. The worst of these side effects was Adobe Illustrator and InDesign failing to make good decisions when converting a Pantone spot color to process color.
I encounter this issue very often and see young designers struggle with it. The consequences of handling color poorly are serious: Inaccurate color reproduction can be a costly mistake in print, and if you’re a logo designer who has released logo files with inaccurate color to a client, it can be a marathon to chase them down and squash them out, replacing them with correct files.
The process should be simple, and you ought to be able to trust software to do this seamlessly: Select a spot color, edit the color, change it from spot PMS to process color, and get an accurate result. The problem is that both InDesign and Illustrator make their color conversions using their own estimates of a color’s on-screen value, disregarding Pantone’s recommendations for how to best reproduce their spot colors in four-color process. And the results are almost always wrong.
Understand the difference between spot and process color.
First, it’s critical to understand what “spot” or “PMS” color means compared to “process” color or “four-color.”
Spot, PMS or Pantone color refers to Pantone’s color matching system, which was developed in the 1950s to help standardize colors across different print houses. Think of them like paint colors from your favorite home improvement store. There are thousands of colors, each assigned a number, and each color is made from a specific mix of base colors that can be matched easily, no matter if you’re printing in Seattle or in Sydney. Printing isn’t an exact science, but PMS colors are the closest the industry has to perfecting the art of color matching. PMS colors are solid ink, so if you look at a PMS color using a loupe, there is no dot pattern, only solid color.
Process color, or four-color printing, is a printing process that utilizes four base ink colors: cyan (c), magenta (m), yellow (y), and black (k). Blending those four colors on paper is how magazines, newspapers, and many brochures/posters achieve color. The color gamut (the range of colors that can be achieved) is much smaller with process color, so matching a PMS spot color in four-color can often be a challenge. If you look at a four-color image using a loupe, you’ll see a discernable dot pattern.
Run the numbers.
Let’s take a single spot color as an example: PMS 187. That’s red, and used by many brands. If you had artwork using PMS 187 and needed to print it in four-color process, you’d need to change the spot color to a four-color mix. And here’s where your trust in software should be limited, and where you should proceed with caution.
Take a look at how Illustrator behaves when we select a PMS 187 color swatch and change it to four-color process.
There should be a warning dialogue box preceding this one that reads ARE YOU SURE YOU WANT TO DO THIS?
If you select a PMS 187 swatch in Illustrator and double-click to edit it, you can change it from a spot to a process color. Illustrator suggests these color values: 22c 100m 89y 15k. InDesign will do the same. But, how accurate of a color conversion is that?
Go by the book.
Now refer to Pantone’s Color Bridge book, which should be on the desk of any print designer. The Color Bridge shows PMS inks alongside recommended four-color equivalents. Pantone recommends these values to achieve the closest color to PMS 187 in four-color process: 7c 100m 82y 26k. Those are radically different (and far more accurate) values than what Illustrator or InDesign will provide.
Want it done right? Do it yourself.
To make this color conversion correctly, InDesign and Illustrator leave you two choices. First, you can look up the correct values in a Color Bridge book, and enter the values yourself.
That’s more like it.
Second, you can open the Pantone Color Bridge Library, find your desired color swatch, and replace your spot color with the bridge color.
With the swatch replaced, be sure to do a save-as so you don’t write over your spot color artwork. If you’re working in Illustrator, use the Select > Same > Fill color and Select > Same > Stroke color to make sure all the instances of the spot color are replaced as you intend.
A sneaky workaround.
I often skirt this issue entirely by creating my own spot color from the beginning. Instead of calling up Pantone swatches in InDesign or Illustrator, I create a new color and name it appropriately. In this case, I’d make a new color swatch, name it PMS 187, assign it cmyk color values of 7c 100m 82y 26k, and make it a spot color. For a printer, as long as they see a separation named “PMS 187,” they’ll know what color is required. And, if you change the color from spot to process, it will retain the CORRECT cmyk values you entered, and you can rest easy.
A great addition to Adobe’s Creative Suite would be an option when changing a spot color to process color: “Use Pantone Bridge recommendation for color conversion?” Until then, do you have any workarounds when converting spot and process color? Have any horror stories to share? Leave them in the comments below.