RGB/CMYK question conversion

[Paul Mc]

Sorry for appearing to ask a question that's been asked before.

This is the first time I've been in this position and I'm not sure what the correct workflow would be. Previous answers on the forums don't appear to help in my specific case.

I've created a print project which was initially specified to be delivered in RGB as it was mainly scanned watercolour art (with vector and text overlays). Now the job has been moved to a new printer and now I need to provide it in CMYK. I'm being asked to use the FOGRA 39 profile.

I've already had signoff from the client on the RGB artwork so I'm hoping I can minimise any pain in going back around that loop again.

Here are the main things I've discovered:

• Setting the profile in the PDF export creates a substantial colour change.
• Changing the document colour profile to FOGRA39 creates a substantial colour change.
• I'm using AD because of the vector work, I notice that in AP there is a document conversion menu option, trying it out caused the same colour shift.

First, are my concerns about the colour shift valid?

Second, what is the correct way to convert the profile and at the same time minimise any colour change?

Here's a small sample where the red component changes noticeably (top CMYK, bottom RGB): 

 

I should probably add that adding the Soft Proof at the top of the layer stack in the RGB document doesn't show a colour change like you see with the profile change.

Also, I fully understand the difference between additive and subtractive colour systems, out of gamut colours and calibrated and wide gamut displays - all of which play a role in how I'm perceiving this shift in colours.  My concern is that I thought (maybe through ignorance) that the colours being used wouldn't be out of gamut as they aren't near the extremes of RGB.

 

[Joachim_L]

8 hours ago, Paul Mc said:

First, are my concerns about the colour shift valid?

Yes, they are because of the nature of the beast. You cannot transfer a wider colour space to a smaller colour space without colour changes. Some colours work better like the green tones, more vivid colours are more difficult to adapt. Seeing your image gives me a little surprise as I would have expected, that the reds would transfer better.

8 hours ago, Paul Mc said:

Second, what is the correct way to convert the profile and at the same time minimise any colour change?

You convert it and have to adapt the colours. In your case you can do this with a Selective Colour adjustment on that image.

But what still strikes me are the red tones. I opened your file and converted to Fogra 39 and had not such a colour distortion. Could you upload the orginal image zipped? Zipped, because the forum software processes the images (e.g. JPG) during upload.

[Paul Mc]

Thanks @Joachim_L I continued my research last night and also found a possibility that the original scanner software may have a part to play in the how the colours now look. I'm going to eliminate that first.

I knew about the intersection of the gamut domains, but like you, was surprised at how far the reds moved. Selective Colour sounds like a good option for manually tweaking the colours within the new profile.

I will prepare a sample and upload shortly.

[Paul Mc]

I think I've got to the bottom of the severe colour change. The watercolour flower objects have a Recolour Adjustment on them to ensure they are all the same hue. This appears to have made things worse when applying the new colour profile. I'm assuming from what I see that the profile conversion is effectively a pre-processing stage and so will present different source colours to the Recolour Adjustment making the result less predictable and not what was intended. The greenery objects didn't have any treatment on them and so explains why they are closer to the RGB original. I think I have something more acceptable now that I can send to the printer so I won't post a sample file.

This arrangement of the layers seems to work well

This also (probably) explains why the Soft Proof didn't show the same change as the Profile Conversion.

So the lesson learned is that Layer adjustments can become a little unpredictable after a profile conversion.