PMS Book not matching InDesign PMS builds
This whole subject causes a lot of confusion. Some possibly useful points:
Keep in mind that the Solid to Process Libraries define colors less precisely than the Solid Coated and Solid Uncoated libraries do. The latter colors are defined colorimetrically, in L*a*b* numbers, and the definition is independent of variations in printing conditions or substrate. It is assumed in this case that one is actually mixing this color and printing it with its own plate. The former, on the other hand, are simply approximations of the color "recipe" one would need to match this color's appearance in CMYK. It's a guess, and the exact numbers would vary depending on printing conditions and substrate choice. So just because you may match the C, M, Y, and K percentages doesn't at all mean that the printed colors will match.
Try this experiment:Using the Color Picker find your color in the Solid Coated library. Note the CMYK equivalent percentages. Close the picker. Now go to your Edit menu and open Color Settings. Change your default CMYK color space. Now look up your spot color again. Notice the CMYK percentages are now different? This is because you've changed the assumed target press conditions. At the same time, the numbers that describe the color appearance, the L*a*b* numbers, have not changed. Think about this.
Summary: If you are calling out the same SOLID spot color, not process equivalent, you are defining the same color. If you are calling out a CMYK process equivalent, you may not be. The latter depends on what press conditions have been specified and what version of the Solid-to-Process Library you are using.
Finally, in actual printing, 3- or 4-color pastels are notoriously hard to match with precision. On the other hand, if an extra plate is used, the ink will be mixed to match and verified by an ink drawdown, and that is a relatively easy way to get the color right.
Mike Strickler
MSP Graphic Services