Advice for RBG > CMYK conversion

[Scott Falkner]

I have been given an RGB Illustrator file based on a stock vector illustration. It is RGB and uses a lot of purples and pinks. I need to convert to CMYK for printing on a digital sheetfed press. I have no more information about the press than that, but I am told they require a CMYK file. I am dealing with a designer, not the printer. The designer may not be dealing with the printer either, just working though their client. I really don't know.

The file uses swatches, thankfully. So I painted each swatch into a Photoshop file and used its much more robust Convert to Profile feature to convert those swatches to CMYK. I am hoping to preserve as much of the saturation and contrast as possible.

Before

After

It's definitely losing something in the conversion, which is unavoidable.

I fear this is the best I can do, but if anyone has a better method, please let me know. Can provide AI file.

[Mylenium]

Your conversion is muddied up with blacks. That is not an acceptable result. The rest should not be an issue, but since it involves blending tricks and faint transparencies therte's probably no point in trying to "convert" the colors. Rather it seems more efficient to simply reconstruct them from scratch by defining your own colors in AI. Assuming your system is reasonably color managed, there should be no issue with that at all and you should definitely get much brighter colors. Of course you may also have to actually cut the overlapping regions into separate pieces to be able to mimic the automated result of the blending by tweaking your colors without blending modes.

Mylenium

[Ton Frederiks]

https://forums.adobe.com/people/Scott+Falkner  wrote

So I painted each swatch into a Photoshop file and used its much more robust Convert to Profile feature to convert those swatches to CMYK. I am hoping to preserve as much of the saturation and contrast as possible.

Illustrator uses exactly the same profiles and algorithms for Color Management as Photoshop.

I would not know how the Photoshop conversion would be more robust.

I am afraid that, without having the profile from the printer, that this is what it is.

You can try to change the Intent in the Color Settings to Saturation.

[Scott Falkner]

Photoshop has more controls for converting to CMYK. Edit > Convert to Profile offers far more options than Illustrator’s File > Mode > CMYK.

[Ton Frederiks]

https://forums.adobe.com/people/Scott+Falkner  wrote

Photoshop has more controls for converting to CMYK. Edit > Convert to Profile offers far more options than Illustrator’s File > Mode > CMYK.

Where?

[Scott Falkner]

https://forums.adobe.com/people/Ton+Frederiks  wrote

https://forums.adobe.com/people/Scott+Falkner   wrote

Photoshop has more controls for converting to CMYK. Edit > Convert to Profile offers far more options than Illustrator’s File > Mode > CMYK.

Where?

For one thing there is no Custom CMYK in Illustrator. Custom CMYK is a killer feature, especially when working with screen captures and scanned drawings. Second, the fact that the conversion requires two commands (one for Color Settings and one to convert to CMYK) is not intuitive. Also, the changes to Colour Setting appear to be application wide, not document specific, which is absurd. I may be wrong about this.

Colour profiles still seem a bit like voodoo to me. That’s why Photoshop’s method just makes sense: I don’t change an application-wide setting (that should not be an application wide setting) and then do a thing. I just do a thing.

[Ton Frederiks]

I would not recommend to convert RGB vector content to CMYK in Photoshop because it is more intuitive. You will lose the resolution independence of the vectors and give it a specific resolution.

The custom CMYK you mentioned is based on outdated technology from the early years of Photoshop.

Did you ever try to use that?

It is not using any of the standard CIE based ICC color management technology and is probably still there for legacy workflows.

But if you really want to create your own custom separation settings, you can create them in Photoshop, save them as a .csf file and load them into Illustrators Color Settings to convert vector content to CMYK.

If you want to do something custom, it will probably require more than just a few clicks.

[Scott Falkner]

I‘m not converting to CMYK in Photoshop. I’m using Photoshop to convert the swatches to CMYK then plugging the colour values into the Illustrator converted file. 

[Ton Frederiks]

There is no reason to make it more complicated by using Photoshop to convert swatches to CMYK when you can do the same in Illustrator.

[Ares Hovhannesyan]

There are a lot of settings for controlling black in Illustrator. You can find them in Recolor artwork, in Black Appearance in Preferences and also in Edit Color.

Illustrator Tutorial: Change the appearance of CMYK black - YouTube

CMYK / RGB to Pantone | Converting colours in Adobe Illustrator - YouTube

Other settings are in Flatten Transparency where you can control Raster and vector settings.

I can suggest to convert RGB to CMYK in Illustrator and then tryto change the black settings.

At the end print to Adobe PDf and see what you get.

[jdanek]

I'd need to know what .icc profile the RGB is tagged with and your color settings before making any recommendations.  However, in my experiences, if you start with an Adobe RGB and convert to SWOP Coated v2 CMYK the file will be a close match.  You should proof ( hardcopy print ) the file before going to press.  Screen view may not be accurate.

[Luke_Jennings]

I would try to convince the designer it's necessary to use two spot colors.

Oops, I see this is on a digital press, well, some digital presses can run spot inks.

[Stephen_A_Marsh]

You will probably have to take a guess that “some form of SWOP” will be the simulation space set at the digital printer…

Not all CMYK profiles are created equal, even within the same colour space. Then there are different rendering intents. There is also the possibility to converting into “any” CMYK space, then assigning a SWOP profile to see how it looks. One can also assign different RGB profiles to the original, changing appearance – and not caring, as it is a means to an end – a better CMYK conversion.

In practice it does not really matter what CMYK space you use for such abstract art, the idea will be to maintain saturation and distinction between the hues. End viewers/users of the printed product will not judge or know or even care what the original RGB looked like – but they will judge the final result. I’m pragmatic, do whatever it takes to get the best final result, your competition will and it does not matter to the client whether you followed best practice or not, they just want the best result possible.

This will often be subjective as to what is considered “better”. Your CMYK conversion at the top, one of many possible CMYK versions below (the lower image actually only uses cyan and magenta):