CMYK to RGB

[Michael5ED9]

One of my clients needs the RGB equivalent of the CMYK palette that was created for their corporate brand. I used an online converter for, eg, grey colour. This is C65, M60, Y55, K39 and converts to R54, G62, B70 yet when swapped the same RGB value becomes C23, M11, Y0, K73. So in InDesign Swatch Options the RGB is R76, G71 and B72. 

I get it's to do with gamut and different conversion tables but cannot grasp why the conversions are so contradictory. Perhaps, investing in the more accurate Pantone color matching system would be a good idea?

Any help will be apprieciated.

[c.pfaffenbichler]

You omitted to mention the Color Spaces so instead of concerning yourself with Pantone Spot Colors (which would likely increase printing costs) you may want to read up on Color Management. 

[Michael5ED9]

Thanks for getting back. I'll do that but this was meant to have been in InDesign discussions. My apologies.

[c.pfaffenbichler]

One important point here: 

While one particular color impression may correspond to one set of RGB-values (if the Color Space is defined) in a CMYK-Color Space more than one set of CMYK-values may share the same appearance. 

Which value is used in conversion from a profiled RGB-image would depend on the Color Spaces’s TAC and GCR (or UCR). 

Edit: … and Render Intent etc.

What are the RGB- and CMYK-Color Spaces in your scenario? 

[Michael5ED9]

These are the color settings selected in Bridge: (which, and embarrassed to admit,but thanks to your question just set 😞

[c.pfaffenbichler]

Did you choose those settings on purpose? 

And do all the involved documents share them or do they have embedded, differing Color Spaces/ICC Profiles? 

[Michael5ED9]

Yes the same and shared with the Creative Cloud apps that require them. I did choose them on purpose but might be a good idea to confirm them with my main printer, perhaps?

[c.pfaffenbichler]

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might be a good idea to confirm them with my main printer

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Yes. 

And if the online converter does not offer Color Space selection is the results are essentially meaningless; is is likely that sRGB is assumed but a FOGRA target space? 

Not quite as likely. 

[Test Screen Name · Accepted solution]

To convert CMYK to RGB you need to know WHICH CMYK and WHICH RGB. if you choose different CMYK or RGB spaces you'll get different answers. And if you don't choose, it's going to be wildly random. Finally, if you use an online converter, or Pantone book, you will get useless made up numbers. Really, these sites are made by people with no clue. 

[Michael5ED9]

Thanks. Yes always about their accuracy.

[davescm]

It's not accuracy of conversion so much as unspecified references. Without a specified color space, colour values in RGB or CMYK mean nothing at all. You might as well say 'orange-ish.'  Very few of those online sites specify a color space to reference and give specific meaning to their values.

That is why you were being asked which CMYK and which RGB colour space. 

Dave

[rob day]

@Michael5ED9  reposted the same question here:

https://community.adobe.com/t5/indesign-discussions/my-client-wants-rgb-values-for-word/td-p/1312426...

[NB, colourmanagement]

You can convert colours from CMYK to RGB in Photoshop, BUT you DEFINITELY need to know the colour space (ICC profile) for each, CMYK AND RGB

I hope this helps
neil barstow, colourmanagement net :: adobe forum volunteer:: co-author: 'getting colour right'
google me "neil barstow colourmanagement" for lots of free articles on colour management