Should I convert RGB colours to CMYK?

RGB colours may look good on screen but they will need converting to CMYK for printing. This applies to any colours used in the artwork and to the imported images and files.

If you are supplying artwork as a high resolution, press ready PDF then this conversion can be done when creating the PDF. If you are supplying artwork in its original format, such as InDesign or QuarkXPress, then it is better to convert colours to CMYK before supplying artwork and files. This will not only give you a better idea of how the colours will look when they are printed but will avoid any problems with colour shifts that may occur.

How to convert RGB colours when creating a PDF

Fortunately in Adobe Acrobat, unless you are also using spot colours*, this is as easy as changing the output options. As shown below, select ‘Convert to Destination’ for Colour Conversion and then select the Destination profile that your printer requires, in this example ‘Coated Frogra39 (ISO 1267-2:2004)’ is selected.

*If your artwork also contains spot colours that you want to print as separate plates, then make sure that you use the setting ‘No Colour Conversion’. Any RGB colours will need to be converted to CMYK in your artwork.

Converting RGB colours in Adobe Acrobat Pro 

How to check for RGB colours in Adobe InDesign

InDesign will flag any RGB colours and images when you package the files to supply the artwork. Check the 'Summary' for an exclamation mark next to ‘Links and Images’ (as shown below). Then, select ‘Links and Images’ in the menu on the left to see a list of files or objects that are using RGB colours.

Checking for RGB colours in Adobe InDesign 

List of RGB images and files

Images will need to be opened in an image editor like Adobe Photoshop, converted to CMYK and then saved. Any imported files will also need opening in their original software, changing to CMYK and resaving.

Objects or text that are coloured in InDesign may not be show in this list. To check for these, a simple Preflight check can be set up in InDesign to scan the artwork for RGB images, objects and fonts. An example is shown below, more details on how to do this can be found on the Adobe website.

Setting up Preflight check in Adobe Indesign 

If you are using QuarkXPress, you will need to follow a similar procedure to InDesign and convert all of the images, files and swatches before supplying artwork.

Following these guidelines should help minimise any colour problems or unexpected results.

At Swallowtail Print any supplied files will be put through our RIP for checking and processing. If you would like more details about supplying us artwork, then get in touch with one of our production team.

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