Pantone specifies ideal (target) values for each Pantone color in Lab.
Most people never think about the fact that when they see CMYK values for any specific Pantone color, those numbers were derived from the target Lab values on the basis of a specific print condition: specific CMYK inks on a specific CMYK press, on a specific substrate, with specific dot gain, etc. So any CMYK values for a Pantone color just represent the best that could be achieved with the specific print condition used to derive the CMYK numbers.
It’s unclear what the original reference condition was for the CMYK characterization used to generate specific Pantone CMYK recipes. Even if you could measure a Pantone color on sheets from the original reference Print Condition used to come up with the CMYK values, it wouldn’t necessarily be the case that the CMYK Pantone swatch exactly matched the target Lab value Pantone was aiming for (the “ideal” Pantone color).
The CMYK values given for any Pantone color are really just a best match to the ideal Pantone Lab value that could be achieved on a specific print run; and in many cases, those CMYK values represent a “dumbed down” rendition of a target Pantone Lab value.
The gamut of a digital press is generally larger than offset CMYK, so a digital press should be capable of hitting more ideal target Lab values for specific Pantone colors. The color transform in the DFE of the digital press should take this into account and, where possible, should be able to represent specific colors more accurately (closer to the ideal Lab value) that a CMYK press.
So when you run from Lab directly to the digital press, you should be able to achieve a better match for many specific Pantone colors than any “hard-wired” CMYK recipe.
Also note that there are different target Lab values for each Pantone color, depending on the Measurement Condition. Pantone supplies vendors with different M0, M1 and M2 Lab target values for each PANTONE+ color (which different vendors choose to implement or not).
You’ll get different results if you measure the same print sample in M0, M1 or M2 mode, so you should be using the right target Lab values for each measurement condition. (But most vendors don’t give you the opportunity to choose.)
For instance, measurement conditions are not currently specified for Pantone Lab libraries used in Creative Suite, but if you look up the values, you can see they are M2 values, whereas the world is moving to M1 as the standard measurement condition (eg. latest FOGRA or GRACoL standards). So it may be the case that the Pantone swatch Lab value was specified for a different measurement condition than the CMYK swatch, and would then produce a different result.
At any rate, if you want to achieve the largest gamut and reproduce Pantone most accurately on your digital press, you should be using the Pantone Lab libraries and let your press DFE do the conversion to the printer space.
