How to change transparency from RGB to CMYK

[Samuel Designer]

Sometimes I help companies with print ads. Today I received an ad and it had colour format CMYK/8, but when I exported it to PDF and send it to the newspaper I got the following error message: "RGB color is used for transparency group". The newspaper does not allow RGB at all, only CMYK, in ads.

I found the "problem", a transparent rectangle that I attach to this thread. I can not find how to change the transparency from RGB to CMYK for this vector i Affinity Designer. 

How do I change the transparency from RGB to CMYK?

 

test.afdesign

[Dan C]

Hi Samuel Designer,

Welcome to the forums

I've downloaded your file attached and it contains 2 objects, both of which have colour fills. I then added a transparent rectangle without a stroke to the design, exported to PDF using the 'For Print' preset and then opened this in Acrobat, below is the preflight analysis for 'Digital Printing (colour)' which shows no errors and the correct colour space.

Could you please provide a copy of the original .afdesign & PDF to the following link?

https://www.dropbox.com/request/AZ1xdahWYRQ8hWLTGHIL

[Samuel Designer]

Hi Dan and thanks for looking in to my problem.

I can not send you the original ad because it is not mine. But I have done some testing and it is only the transparent white bar that is causing problems. I will attach a pdf I exported from the afdesign file and a screenshot from when I upload it to the newspaper and get an RGB warning.

A friend who use Adobe Creative software was able to export the PDF without a RGB warning. So I know that Adobe software is able to change RGB transparency to CMYK. Can Affinity Designer?

test2.pdf

[R C-R]

21 hours ago, Samuel Designer said:

But I have done some testing and it is only the transparent white bar that is causing problems.

I am a bit puzzled by what you mean by your reference to a "transparent white bar." I thought that in the CMYK color space, anywhere there is no ink is as close to transparent as you can get, so for printed output the color of the paper is all you see there, whatever color that might be.

[Samuel Designer]

Hi R C-R,

In the original ad there is a image behind the white transparent bar and then some black text above the bar. But right now it does not mater: Affinity Designer is not exporting everything as CMYK, some parts - like transparency - is still exported as RGB. This problems does not exist white Adobe Creative software because my friend who use that have no problems exporting the transparent bar as CMYK (no RGB!).

I need to find out how to save an ad in Affinity Designer without RGB transparency! 

 

[R C-R]

37 minutes ago, Samuel Designer said:

In the original ad there is a image behind the white transparent bar...

I still do not understand what you mean by "white transparent bar." If something is 100% transparent, it has no color at all. It is not white or any other color.

Also, in the CMYK printing process, there is no way to 'print' white because there are only four ink colors & no combination of them will produce white.

[MikeW]

3 hours ago, R C-R said:

I am a bit puzzled by what you mean by your reference to a "transparent white bar." I thought that in the CMYK color space, anywhere there is no ink is as close to transparent as you can get, so for printed output the color of the paper is all you see there, whatever color that might be.

Download the test.pdf and open it in Acrobat and you'll know what is being talked about.

The "bar" is a rounded rectangle with transparency but it is not 100% transparent.

Here I am using Acrobat's Object inspector and you can see that the bar/rectangle itself is a CMYK construct, but its transparency space is RGB.

The PDF itself is using an RGB blend space as can be seen in this screen shot as well.

[R C-R]

3 minutes ago, MikeW said:

Download the test.pdf and open it in Acrobat and you'll know what is being talked about.

I don't have Acrobat so I was just going by what @Dan C said he got with that app.

[Wosven]

We usually use PDF X-1a to avoid transparency, that can cause havoc in printed documents if different profiles are used. It will flatten each part using transparency.
It shouldn't be a problem if your PDF is a the expected size (it won't be enlarged later).

Another quick solution if your document is as simple as your example (plain colours an not a lot of transparent area): you can fill the white and transparent object with the resulting mauve colour at 100%: no more transparency.

It would be interesting to know which PDF version using transparency keep on using RVB until we're able to specify a profile to transparency or know how to avoid it when exporting to CMYK.

[MikeW]

20 minutes ago, R C-R said:

I don't have Acrobat so I was just going by what @Dan C said he got with that app.

Dan ran a preflight that would not reveal the issue. 

[Samuel Designer]

2 hours ago, MikeW said:

Here I am using Acrobat's Object inspector and you can see that the bar/rectangle itself is a CMYK construct, but its transparency space is RGB.

Well thank you MikeW! Now we know what is wrong - the document is using "ICCBasedRBG, sRGB-IEC61966-2.1". Why is it doing this? I'am exporting the document as CMYK. Can the Affinity crew fix this in the software?

[Samuel Designer]

2 hours ago, Wosven said:

We usually use PDF X-1a to avoid transparency, that can cause havoc in printed documents if different profiles are used. It will flatten each part using transparency.
It shouldn't be a problem if your PDF is a the expected size (it won't be enlarged later).

Another quick solution if your document is as simple as your example (plain colours an not a lot of transparent area): you can fill the white and transparent object with the resulting mauve colour at 100%: no more transparency.

It would be interesting to know which PDF version using transparency keep on using RVB until we're able to specify a profile to transparency or know how to avoid it when exporting to CMYK.

Hi Wosven! Thanks for your input 

Exporting the ad to PDF/X-1a:2003 solved the problem!!! The X-1a file was approved (no RGB transparency warning) when uploading it to the newspaper, and it looked OK and had transparency.

Previously I had exported with "PDF (for print)" and "PDF (for export)", but it keeps RGB in the PDF.

Have a great day Wosven! 

[MikeW]

1 hour ago, Samuel Designer said:

...

Exporting the ad to PDF/X-1a:2003 solved the problem!!! ...

Because the rounded corner rectangle becomes flattened (i.e., a bitmap) there is no longer transparency and thereby having no transparency blend space at all.

PDF/X-4 will maintain the transparency, set the transparency blend space to CMYK and set the document output intent to your ISONewspaper26v4 profile. However, some print services do not like having the destination output intent embedded if they are complying to the more modern GHENT Working Group recommendations.