Colour Management: RGB vs CMYK
Why do vibrant screen colours look dull in print? Learn the difference between RGB and CMYK, when to use each, and how to get consistent colour results.
Colour Management: Why Screen Colours Don't Match Print
The most common disappointment in print production is: "The colour looked great on screen, but came out dull on paper." Understanding why this happens — and how to prevent it — is the most valuable thing you can learn about print-ready file preparation.
RGB vs CMYK: Two Completely Different Systems
| RGB | CMYK | |
|---|---|---|
| Used for | Screens, monitors, web | Printed materials |
| Colour mixing | Additive (more light = brighter) | Subtractive (more ink = darker) |
| Range | Very wide — neon, fluorescent colours possible | Narrower — cannot reproduce neon |
| Output | Digital display | Physical print |
Always design in CMYK for print
If you design in RGB and then convert to CMYK, colours can shift by 15–20% (measured as Delta-E). Neon greens become olive; vivid blues become muted. NowToPrint reports the RGB risk, preserves the PDF, and leaves the actual colour conversion to the downstream RIP/DFE. Start in CMYK from the beginning when colour intent is critical.
ICC Colour Profiles
An ICC profile tells the press how to interpret your CMYK values based on the paper type:
| Paper type | Recommended ICC profile |
|---|---|
| Coated / gloss | FOGRA39 (ISO 12647-2) |
| Uncoated / matt | FOGRA47 |
| Newspaper | SNAP 2007 |
When exporting your PDF, set the Output Destination to the correct ICC profile for your chosen paper stock. NowToPrint's preflight engine checks that an ICC profile is embedded.
Spot / Pantone Colours
If your brand has a precise colour that must never vary — such as a corporate logo colour — CMYK may not be able to reproduce it accurately enough. In these cases, use Spot (Pantone) colours, which are pre-mixed inks supplied directly to the press.
- Spot colours have a higher unit cost than CMYK.
- Not all print products support spot colours — check with the order configuration.
Total Ink Coverage (TIC)
The sum of all four CMYK channels (C + M + Y + K) must not exceed 300%. If it does, paper becomes oversaturated with ink, which cannot dry properly and smears onto adjacent sheets.
Example of an illegal value: C:100 + M:100 + Y:100 + K:100 = 400% → rejected by preflight.
Rich Black for Large Dark Areas
When filling a large background with black, using K:100 only often looks flat and grey. For deep, rich backgrounds use:
Rich Black formula: C:60 / M:40 / Y:40 / K:100 (total: 240% — within the safe TIC limit)
Never use Rich Black for small text or fine lines. At press speeds, multi-ink registration can shift by fractions of a millimetre, causing coloured halos around thin letterforms. Small text must always use K:100 only (C:0, M:0, Y:0).
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