Venky Designs — Design production specs for print | venkydesigns.com
Use RGB for anything that stays on a screen and CMYK for anything that goes to press — and do the conversion yourself, before export, while the shift is still free to fix.
The two modes build color from opposite ends. RGB starts from a black screen and adds red, green and blue light until it reaches white; CMYK starts from white paper and lays down cyan, magenta, yellow and black ink until it reaches black. One is emitted light, the other reflected light, and the range of colors each can show — its gamut — only partly overlaps.
Print has a physical ceiling screens do not. Because CMYK builds color from inks up on white paper, total ink coverage is usually capped at 260-300%: past that point too much wet ink sits on the sheet and it cannot dry properly on press. A monitor has no equivalent limit, so the most saturated screen colors simply have no printable equivalent.
On narrow screens, swipe or scroll the plate sideways.
Saturated blues are the classic casualty. A vivid screen blue sits outside the CMYK gamut, and on conversion it is remapped to the nearest printable mix — which is duller and often drifts toward purple. Designers who convert before export see this happen and can choose a better printable blue; designers who leave conversion to the printer discover it on the proof.
Viewing light adds a second shift on top of the first. Proofs are judged under D50 (5000 K) light; the same sheet reads cooler under 6500 K daylight and warmer under 2700-3000 K office bulbs. Approving a CMYK conversion on a backlit RGB screen and then reading the sheet under office lighting stacks both shifts at once.
The working rule that ties this page back to the rest of the guide: design, convert to CMYK before export, keep total ink coverage under the cap, and judge the proof under D50. Resolution math for the same file is covered on the homepage, the container choice on the Print File Formats page, and the full ordered pass on the Print Preflight Checklist page.
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