CMYK vs RGB: Why Print Colours Shift
The difference between mixing light and mixing ink — and why a screen can show colours a printing press physically can't reproduce.
RGB and CMYK are two ways of describing colour: RGB mixes light and is what every screen uses, while CMYK mixes ink and is what printing presses use. That single difference is why a photo that glows on your monitor can come off the printer noticeably duller — a screen can emit saturated colours that ink physically cannot reproduce.
Additive vs subtractive: the actual difference
RGB is additive. A screen starts black and adds red, green, and blue light; turn all three up full and you get white. CMYK is subtractive. Paper starts white and each layer of cyan, magenta, or yellow ink absorbs some of the light bouncing off it, so the more ink you add the darker it gets. The K is black (the "key" plate) — cyan, magenta, and yellow together make a muddy brown rather than a clean black, so print adds a dedicated black to get crisp text and deep shadows.
Why the web is RGB
Screens make colour by emitting light, so they are additive by nature, and the web is built on RGB from top to bottom. The image formats it runs on reflect that: PNG, GIF, and WebP store colour as RGB and have no CMYK mode at all. JPEG is the one format that can technically hold CMYK data, but browsers handle it inconsistently — a CMYK JPEG often shows up online with wrong or washed-out colours. For anything headed to a screen, RGB is the only safe choice.
Why the printed version looks duller
CMYK's range of reproducible colour is narrower than RGB's, especially for bright greens, oranges, and vivid blues — those sit outside what cyan, magenta, and yellow ink can mix. When a design app or a printer converts your RGB file to CMYK, any colour it can't reach gets pulled in to the nearest printable one, and the image loses a little punch. Nothing is broken; the ink simply can't get there, the same way a screen can't reach a colour brighter than its backlight.
Quick comparison
| RGB | CMYK | |
|---|---|---|
| Mixes | Light (red, green, blue) | Ink (cyan, magenta, yellow, black) |
| Starts from | Black (screen off) | White (blank paper) |
| Add more and it goes | Brighter, toward white | Darker, toward black |
| Best for | Screens, web, apps | Physical print |
| Colour range | Wider (more saturated colours) | Narrower |
What this means on babapic
babapic works entirely in RGB, and so does everything it produces. Its tools run on your device's canvas, which is an RGB surface, so opening any image here gives you an RGB result — useful if a stray CMYK JPEG is displaying with the wrong colours and you just want a clean RGB copy for the web. What babapic does not do is output print-ready CMYK. Converting a file to CMYK for a press belongs in the design app that made it (Illustrator, InDesign, Photoshop) or with the print shop, both of which let you preview the gamut shift and choose how colours map. No browser-based image tool can do that honestly — it's the same reason colour-space conversion isn't a babapic tool in the sRGB guide.
Getting an image ready for the web
Once you know you're staying in RGB, the usual upload prep applies, and it all runs on your device with nothing uploaded:
- Match the format to where it's going — JPG or PNG, via PNG to JPG or JPG to PNG.
- Bring the pixel count down to what the page actually displays — Resize Image. Oversized files are the usual reason an image is so big.
- Fit a size limit if the form has one — Compress Image.
FAQ
Should I use RGB or CMYK for my website?
RGB, always. Screens are RGB devices and web formats are RGB; a CMYK file uploaded to the web can display with wrong colours. Keep web work in RGB and only convert to CMYK for physical print.
Why do my colours look duller when printed?
CMYK ink covers a smaller range of colour than a screen emits, so the brightest greens, oranges, and blues shift toward the nearest printable version during the RGB-to-CMYK conversion. Previewing in CMYK inside your design app before printing shows you the change in advance.
Can I convert RGB to CMYK online here?
No — babapic is RGB-only, like any browser-canvas tool. For print-ready CMYK, use a design app (Illustrator, InDesign, Photoshop) or let your print shop handle the conversion, so you can control how out-of-range colours are mapped.