CMYK Blues. It’s pretty easy to ensure that Web colors look correct, since the computer is both the medium used to pick the color and the one displaying it. When it comes to calculating and displaying CMYK color, however, computer-generated values and their display can be a disastrous combination. Here are some details.
Color Calls. Let’s say you are looking for a color, and you start with a color picker on the web or in a desktop application such as Photoshop or InDesign. You pick your color and it magically displays the RGB value and the CMYK value. It’s not quite that simple. Color picker values are accurate for RGB, but can be wildly misleading when transformed into CMYK “equivalents”. Here’s how to avoid that risk.
The basic premise of this article is that print colors are best specified from printed color guides. A printed guide reflects the realities of ink pigmentation, paper brightness and all of the other factors inherent in how colors reproduce.
There is a larger problem with choosing CMYK colors from so-called Color PIckers like those you will find on the Web. These tools use mathematical formulas to convert the color you select to the color you want. Good in theory but in practice, the best color conversions come from color look-up tables (CLUTs). CLUTs are sets of color mappings where the values are stored in a table or database rather than being calculated on the fly. It’s the method used by high-end scanners and the reason why they generate superior color.
Conceptually, a good example of a color look-up table is the Pantone solid to process color guide. It provides maps the colors of the Pantone Solid Color Guide to their closest CMYK match, providing the CMYK values for each right on the swatch.
Pantone color guides are built into Photoshop. With this capability, you can start with a color picker and map the color to the closest Pantone solid to process color swatch. This allows you to choose the color you want while giving you a predictable standard in the resulting values specified. Here’s how.
1. Open Photoshop and create a new blank document in CMYK format. Click on the foreground color picker tool at the bottom of the toolbar.
2. Choose the color you want from the Color Picker. Since the Color Picker is a screen-display it is inherently RGB. Notice that Photoshop provides an on-the-fly CMYK value. Ignore this value and instead click on the Custom button after you have selected a color from the color picker.
3. Choose Pantone solid to process coated from the Book pull-down menu. Photoshop will automatically select the Pantone swatch that is closest to the color you selected, and displays the corresponding CMYK value of the Pantone swatch. Notice in our example, the default generated CMYK is 97C 93M 44Y 27K while the Pantone value is 76C 78M 0Y 47K.
We guarantee that in the vast majority of instances, you will find the Pantone solid to process color far superior to the CMYK value generated by default.