Please let me tell you my very personal opinion:
Pantone should be used only if Pantone spot inks have to be printed, never
never as a design guide. The inks are mixed according to Pantone recipies.
Here one needs two swatch books (paper fans): one for coated paper, the other
for uncoated. The mixture of Pantone inks is based on assumptions of Pantone
(the company): the printing process and the kind of paper for coated and
uncoated. If the actually used paper is different, then the print results as
measured by Lab will be slightly different.
For CMYK printing one needs two swatch books: one for coated paper,
the other for uncoated, valid for the most representative printing process in the
respective country, for instance ISOCoated-v2-eci (don't mind different spelling).
It seems that people forgot the existence of these swatch books. They cannot
be replaced by computer simulations.
If Pantone colors (not inks) should be reproduced by CMYK, then the most
promissing method is in my opinion: get the Lab values and convert them in
Photoshop into CMYK values for the actually chosen and valid CMYK space.
This will fail – considering the result – if the Pantone colors are out of gamut
for this CMYK space. Then a re-design is necessary.
Alternatively measure Lab values in the actually used Pantone swatch book
(which may be outdated) and convert them by Photoshop into the relevant
CMYK space. Measuring requires an instrument, for instance X-Rite DTP22,
for me the good old work horse.
IMHO, all ready-made conversion tables between Pantone and CMYK should
be ignored: outdated Pantone definitions (even the Lab values are 'drifting' as
time goes by) and dubious CMYK printing conditions.
Best regards --Gernot Hoffmann
Before the computer, Pantone sold their complete Spot color set in swatch books and reference guides. If you wanted to apply a color to an element, you'd choose one from the printed reference guide. Part of their printed reference guides was solid-to-process CMYK equivalents. What very few people understand is, the side-by-side comparison ( Spot vs. CMYK Equivalent ) is not a match. The only reason why Pantone references an uncoated version is show what that specific color would look like on a non-coated sheet. Before the computer, you referenced an uncoated color using an uncoated color chip, which visually does not match a coated chip. So, messy designers would put a coated swatch chip on a mechanical that was meant to be printed on a noncoated sheet. The result? Angry printers like yourself who could not make an accurate determination of what the color was supposed to look like = confusion. Any designer who tells you it is OK to assign a coated swatch to a noncoated printing file is as wrong as they were then as they are now. The computer has only made things more confusing and Pantone has not helped. In an effort to allow applications to better match unmatchable colors, Pantone reformulated their CMYK ( not all ) equivalents and released Pantone Bridge. Then, they reformulated again, and released the + Series. In defense of Pantone, these different reformulations give users the ability to get CMYK colors that may be closer to Spot ( in certain cases ). Let me help your issues...