Editor › Learn › RGB vs CMYK: What Actually Changes When You Convert
What is the difference between RGB and CMYK?
RGB is additive and describes light emitted by a screen; CMYK is subtractive and describes ink absorbing light on paper. RGB can represent colours no press can print, so converting always involves mapping out-of-gamut colours to the nearest printable ones.
The practical difference
| RGB | CMYK | |
|---|---|---|
| Model | Additive (light) | Subtractive (ink) |
| Channels | Red, Green, Blue | Cyan, Magenta, Yellow, Black |
| More value means | Brighter | Darker |
| Typical use | Screens, web, video | Offset and digital printing |
| Gamut | Wider | Narrower, and paper-dependent |
Which colours shift most
- Saturated greens and cyans — screens produce these far beyond ink.
- Bright oranges and pure reds tend to dull slightly.
- Deep blues can turn purple without enough black support.
- Neutral greys shift if the conversion is not profile-driven.
How to convert well
- Finish the work in RGB and keep that file as the master.
- Get the ICC profile for the actual printing condition from your printer.
- Soft-proof with that profile to see the shift before you commit.
- Choose a rendering intent — relative colorimetric for most work, perceptual when large areas are out of gamut.
- Convert, then inspect the plates and the shadow areas.
Why a formula is not enough
A naive conversion computes black as a function of the lightest channel and ignores the press entirely. A profile-driven conversion knows the ink behaviour, the paper, and the total ink limit. That difference is visible in shadows and neutrals.