▰printernational
← Back to librarycolour management

Print fundamentals · 4 min read

Converting RGB to CMYK

A current, profile-aware workflow for preparing RGB photography and artwork for commercial print.

PRIPrinternational
Published 9 June 2010

RGB and CMYK describe colour for different jobs. RGB is built for light-emitting screens; CMYK describes the inks used in process printing. Because a press cannot reproduce every colour a screen can show, an RGB-to-CMYK conversion remaps some colours into the smaller print gamut.

The important question is not simply “Should I convert?” It is who should convert, to which output profile, and when? The answer depends on the printer’s specification and the final print condition.

A calibrated display beside a printed CMYK proof with colour bars
Compare the screen intent with a profiled print proof

Start with the printer’s specification

Ask for the required PDF standard, CMYK output profile, total ink limit, paper stock and proofing process before you convert anything. A profile intended for coated offset stock is not automatically right for uncoated paper, newsprint, digital print or a packaging press.

If the printer accepts a colour-managed PDF with RGB images and embedded profiles, leaving photography in RGB can preserve more editing flexibility and let the conversion happen at the correct output stage. If they request CMYK assets, convert a copy using the profile they supply. Never guess a profile from the job name alone.

Keep the RGB master. Convert a production copy only when the required print condition is known.

Photoshop: soft-proof, adjust, then convert

Photoshop is the right place to make image-level decisions.

  1. Keep the original image in RGB, with its embedded profile intact.
  2. Choose View › Proof Setup and select the printer’s CMYK profile; turn on View › Proof Colors to preview the conversion.
  3. Use the gamut warning to identify colours that will change, then make any tonal or saturation adjustments while you still have the RGB master.
  4. When a CMYK file is specifically required, use Edit › Convert to Profile and select the supplied CMYK destination. Use Image › Mode › CMYK Color only when that is the intended conversion workflow.

The conversion is irreversible for out-of-gamut RGB colours, so save the RGB original separately. Editing first in RGB and converting at the end is Adobe’s recommended general approach.

A printed CMYK proof showing fine halftone dots, colour bars and crop marks
Proof the printed result, not just the on-screen image

Illustrator and InDesign: preserve the workflow

In Illustrator, set the document to File › Document Color Mode › CMYK Color when creating process artwork for print. For existing vector artwork, use Edit › Edit Colors › Convert to CMYK only after confirming that process conversion is wanted; do not accidentally convert intentional spot swatches.

In InDesign, avoid manually converting every placed image simply to make the Links panel look uniform. Build a colour-managed document, preserve embedded profiles, and use the printer’s PDF preset and output profile at export. In the PDF export Output settings, the conversion policy should match the printer’s instruction—often Convert to Destination or No Color Conversion for a managed workflow.

Before you send the file

  • Confirm the PDF standard and output profile with the printer.
  • Check overprint, rich black, spot colours and total ink coverage.
  • Inspect a soft proof, then approve a contract proof when colour is critical.
  • Package the working file and keep the RGB originals, linked assets and final PDF together.

For the fundamentals behind the conversion, read RGB versus CMYK. For image-specific checks, see Photoshop CMYK tips.