When converting a logo from CMYK to rgb, which RGB values should you use?

New Here ,
Apr 24, 2021 Apr 24, 2021

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Hello

 

I've been researching colour management a lot which has led to my question above. I have come across an old logo that has the same rgb values when in CMYK to when it is actually converted to RGB. When looking closely this is due to colour management being switched off.

 

If I take the CMYK version of this logo and operate with colour management on (Europe General Purpose 3), RGB is sRGB and Cmyk is FOGRA39), when I convert from CMYK to rgb, is gives me slightly different RGB values.

 

So, which values should be used for the RGB version of the logo? I assume when ai converts from cmyk to rgb, it gives the closest rgb match to the cmyk?

 

Any help would be appreciated.

 

Thanks

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Draw and design, How to, Print and publish, Sync and storage, Tools

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Adobe Community Professional ,
Apr 24, 2021 Apr 24, 2021

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It depends on what you want to use the RGB for.

If you want to use it for web purposes, sRGB is the right choice.

If you want to use it to print from an rgb document on a color inkjet printer that has more than 4 inks, I would go for Adobe RGB or similar larger gamut RGBs.

Adobe RGB can represent most CMYK colors, while sRGB can only represent a subset.

But it actually depends on the color, some CMYK colors can be represented both in sRGB as well as Adobe RGB (although the numbers will be different).

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Adobe Community Professional ,
Apr 24, 2021 Apr 24, 2021

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All color conversions have to assume both the starting and ending color spaces, even when color management is “off.” When color management is “off” (as in old versions of software before color management was used), the assumed RGB color space is probably the display color space. That is unreliable, because when displays are uncalibrated, each display can have a slightly different color space, even when made on the same assembly line, so a color conversion that matched on one monitor would not match on another.  That’s why everybody started using color management, so that color spaces could be defined and communicated through profiles, which made color conversions more consistent and predictable.

 


@SaintSeabass wrote:

If I take the CMYK version of this logo and operate with colour management on (Europe General Purpose 3), RGB is sRGB and Cmyk is FOGRA39), when I convert from CMYK to rgb, is gives me slightly different RGB values.


 

If you are getting slightly different values, the reason may be that the selected CMYK color space is wrong, the selected RGB color space is wrong, or both are wrong. The only way to match an old CMYK-to-RGB conversion if both the CMYK and RGB color spaces used for the original conversion are known and applied to the current conversion. Changing either color space will change the results of the conversion, so you have to know and use the right color spaces to get the same results. 

 

Matching a very old logo could be a challenge. For example, if the logo was made in the 1980s or 1990s before color management, the CMYK and RGB color spaces used for the conversion might have been both unlabeled and not relevant today. 20 to 30 years ago, the CMYK color space might have been some generic conversion (maybe US Web Coated SWOP), and on a Mac the RGB color space could have been Apple RGB. A problem with Apple RGB is that it represents the color of specific Apple CRT monitors that were last made over 20 years ago (which does not match sRGB), but there is a profile for it. So if you are trying to match a conversion from many years ago, you would want to do some historical research, then based on that you make an educated guess about the most likely CMYK and RGB color spaces used by software at that time, then apply those profiles to your conversion. It may take some testing to figure out what they were.

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