Convert from PMS to CMYK colour

[cje]

I'm in need of converting a PMS colour to CMYK. Can't find how or any forum posts which solve this issue. 

 

[MickRose]

Double click the round fill area in the Colour panel or at the bottom of the Tools panel. That brings up the Colour Chooser. Then change one of the CMYK values, then back again. Easiest way is to use the mouse scrolling button to go up and then down. That changes the fill to CMYK rather than Pantone.

 

[R C-R]

Not sure how much it matters to you but note that as explained here, only a subset of Pantone colors can be reproduced exactly using only the 4 CMYK ink colors.

[lacerto]

It is also good to understand that what is described above by @MickRose is the technical method of converting a PANTONE special ink (e.g., those included in the Formula Guide Solid Coated V5 and Formula Guide Solid Uncoated V5 libraries) to CMYK values, and that this conversion is based on fixed sRGB values defined in the CSV files provided with Affinity apps (and then on the currently active document CMYK profile).

That means first that already the RGB values are constrained into a narrower gamut than necessary which may result in conversion values which produce clearly different colors on paper than definitions based on color profile independent Lab values.

PANTONE provided "official" CMYK conversion values, even when given in context of specific profile and illuminant (like when using the now legacy PANTONE Color Manager) would probably deviate slightly from Lab based color conversions performed by e.g. Adobe apps to specific ISO profiles, but they may nowadays also be given, e.g. in context of PANTONE Connect, as fixed values without such conditionals (and accordingly provide less accurate reproduction of special inks in specific CMYK production environments). 

What is said above applies to PANTONE special inks, which I assume you meant by referring to "PMS colors". Colors of other PANTONE color libraries, e.g. those meant to be produced by using standard inks, may be defined in fixed color values in both sRGB and CMYK (generic), like those in the PANTONE Color Bridge Coated V5 and PANTONE Color Bridge Uncoated V5 libraries provided with Affinity apps, so when using these libraries, their CMYK values will not vary within Affinity apps depending on the target CMYK profile, so the CMYK values would be equal both when using e.g. PSO Coated v3 for glossy media, and when using ISO Newspaper for newsprint. In other apps colors of these libraries, too, are typically defined in Lab so their CMYK conversion values would vary depending on the target profile, similarly as when using special inks.

[cje]

19 hours ago, R C-R said:

Not sure how much it matters to you but note that as explained here, only a subset of Pantone colors can be reproduced exactly using only the 4 CMYK ink colors.

Thank you for your information. 

[cje]

15 hours ago, lacerto said:

What is said above applies to PANTONE special inks, which I assume you meant by referring to "PMS colors". Colors of other PANTONE color libraries, e.g. those meant to be produced by using standard inks, may be defined in fixed color values in both sRGB and CMYK (generic)

Thank you. Good to know.