Transparency Blend Space RGB / CMYK

[tully1254]

There is option in Transparency Blend Space to set Document as RGB or CMYK.

When I close file for print I use one of the Indesign colour profile options (fogra 39).

Will it affect the outcome of the printing if document is set in RGB rather than CMYK?

[Test Screen Name]

Yes. All objects on the page are converted to the transparency blend space at some point, and perhaps back again to an output space.

[rob day · Accepted solution]

There is option in Transparency Blend Space to set Document as RGB or CMYK.

The blend space only affects the preview of a spread that includes any transparent object. It doesn't actually change an object's color, and if there are no transparent objects on the page, it has no affect at all.

A blend space is needed because InDesign allows a mix of RGB, CMYK, or Lab colors on the same page, all of which can be blended together via transparency effects. For postscript print output, the page has to be flattened into a single color space, which is defined by the blend space. The Transparency Flattener preset you choose in the Print dialog's Advanced tab affects how the flattening is handled.

If you export to PDF, the transparency can be kept live and still contain a mix of color modes—the PDF/X-4 preset.

[tully1254]

I am working with a lot of light-up images with colours that look vibrant on screen, and I want to know which PDF setting will maintain as much vibrancy as possible in the printing.

Will the postscript PDF set in RGB colour give better results than exporting?

Or exporting using the PDF/x-4 preset?

[Test Screen Name]

Never use Postscript to make a PDF with InDesign. Just never.

Not sure what level of experience you’re coming from with this. Are you familiar with the CMYK gamut? Are you working with a CMYK profile supplied by your print provider?

[tully1254]

I do have a considerable amount of experience in Indesign, but I am not familiar with the CMYK gamut.

Yes, I am working with CMYK profile the printer has provided - FOGRA39.

[rob day]

Yes, I am working with CMYK profile the printer has provided - FOGRA39.

If the destination is an offset press, you would want to turn on Overprint Preview in order to get a print preview. That will preview all RGB or Lab color, whether there is transparency or not, in your document's assigned CMYK profile's color gamut. Make sure FOGRA39 is the document profile assignment. An existing document's profile assignment isn't necessarily set in Color Settings, check Edit>Assign Profiles...

[tully1254]

Thank you.

I use the correct Color Setting when exporting to PDF. Is it also necessary for the printing to set correct profile in 'Assign Profiles'? Or does this only affect the print preview?

[rob day]

Yes, it is very important to make sure the document's assigned profile is correct. The Color Settings is your preference for setting the color management rules for future documents, and doesn't necessarily have any affect on existing documents.

So if you create a document using one of the default Color Settings presets like North America Prepress, the assigned CMYK profile will be US Web Coated SWOP. If you then export that document with FOGRA39 set as the Destination profile in the Output tab, there will be an extra CMYK-to-CMYK conversion for any CMYK colors you use, which is never ideal and in some cases can cause color output problems.

If the document assignment is FOGRA39, and you choose Document CMYK as the Destination, the document's CMYK values will export unchanged.

Of course none of this solves the problem of out-of-gamut RGB colors being unprintable—if you are using RGB colors you really want to get an accurate proof from the printer.