Converting to CMYK at the start of a project, which clips vivid colours permanently and cannot be undone by converting back.
CMYK
Also called cmyk colour, four colour process or print colours. Here is what it means, when it changes what you export, and what people get wrong.
PrintRuns on your deviceUpdated 10 August 2026
The short answer
CMYK is the four-ink colour model used in printing: cyan, magenta, yellow and key (black). Inks subtract light reflected off paper, whereas screens add red, green and blue light. That difference means some vivid RGB colours cannot be printed, and files need converting before they go to press.
Updated
The short version
CMYK at a glance
| Quick fact | Detail |
|---|---|
| Stands for | Cyan, magenta, yellow, key (black) |
| Model | Subtractive, ink on reflective paper |
| Screens use | RGB, additive light |
| Hard to print | Saturated greens, blues, violets, bright oranges |
| Formats that support it | JPEG, TIFF, PDF (not PNG or WebP) |
| Convert when | At output, using the printer's ICC profile |
Slide the table sideways to see every column.
Why can't a printer reproduce a bright screen green?
Because the two models build colour in opposite directions. A screen starts black and adds red, green and blue light, so all three at full strength give white. Ink starts with white paper and subtracts wavelengths, so cyan, magenta and yellow together absorb most of the light and give a muddy dark brown. Black ink, the K, is added because that mixture is neither black enough nor economical, and because fine black text printed from three inks would never register cleanly.
The set of colours a system can actually produce is its gamut, and the RGB and CMYK gamuts are different shapes rather than one sitting neatly inside the other. Process inks struggle most with the saturated greens, blues, violets and bright oranges that a screen produces easily, and those tend to come back duller and slightly shifted in hue. In a few regions, notably certain cyans and yellows, ink on good stock can reach colours that sRGB cannot.
A gamut warning in an editor is simply flagging the pixels whose colour falls outside the destination profile's range, so you know in advance which areas will shift. Soft proofing goes further and simulates the printed result on screen using the printer's profile.
When should you convert to CMYK?
As late as possible, and only once. Edit and archive in RGB, then convert at output using the ICC profile for the specific press, paper and ink combination the job will run on, with a rendering intent chosen for the image (perceptual for photographs, relative colorimetric with black point compensation for most other work).
Converting early causes two problems. It clips every out-of-gamut colour immediately, and converting back to RGB afterwards does not recover them, so the damage is permanent and invisible until you look for it. It also locks the file to one printing condition, which is wrong the moment the job moves to different paper or a different press.
Ask your printer which profile they want before you convert anything. Many modern print workflows would rather receive a properly tagged RGB file or PDF and handle the conversion themselves, because their RIP knows their press better than your editor does.
What happens if you upload a CMYK image to the web?
Trouble, usually. Browsers, marketplaces and social platforms all expect RGB, and sRGB in particular. A CMYK JPEG may display with badly wrong or inverted colours, be silently reconverted with unpredictable results, or be rejected by the upload validator outright. If your listing photo came back from a designer or a print file, check what colour mode it is in before you blame the platform.
It is also worth knowing which formats can even hold CMYK. JPEG, TIFF and PDF can. PNG and WebP cannot, since both are defined around greyscale and RGB only. That is why exporting a CMYK print file as a PNG forces a conversion whether you asked for one or not. For anything on screen, convert to sRGB deliberately, tag it, and keep the CMYK version for the printer.
What people get wrong about cmyk
Each one is a real failure mode, not a style preference.
Uploading a CMYK JPEG to a marketplace or social platform, where it may show inverted colours or fail validation.
Using a generic CMYK profile instead of the one your printer specified, then being surprised the proof does not match.
Assuming a colour looks wrong because the monitor is uncalibrated, when it is simply outside what process inks can reach.
Questions people ask
CMYK, answered
The follow-up questions people search for once they have the definition.
Should I send my printer RGB or CMYK files?
Ask them. Many commercial printers now prefer a correctly tagged RGB file or PDF and convert it themselves with a profile matched to their press and paper. If they do want CMYK, get the exact ICC profile from them rather than using a default.
Why do my prints look duller than my screen?
Partly gamut, partly light. Ink on paper cannot reach the saturation of a backlit display, so vivid colours flatten. Paper also reflects only the light in the room. Soft proofing with the printer's profile shows you the shift before you commit to a run.
Can I convert CMYK back to RGB?
Technically yes, but the colours lost in the first conversion do not return. You get an RGB file that still looks like the CMYK version, with the out-of-gamut areas still clipped. Always keep the original RGB master rather than relying on a round trip.
Does CMYK work for online listings?
No, use sRGB. Online platforms and browsers are built around RGB, and CMYK files often display incorrectly or fail to upload. Keep CMYK for anything going to a press, and export a separate sRGB version for everything that will be viewed on a screen.
Same cluster
More from the glossary
Neighbouring entries, so every term in the set is one hop from every other.
Clipping path
A clipping path is a vector outline drawn around a subject so that everything outside the line is hidden.
Colour profile
A colour profile is the data attached to an image that says which colour space its numbers belong to.
Chromatic aberration
Chromatic aberration is a lens fault where different wavelengths of light do not come to focus in the same place, leaving coloured outlines along high-contrast edges.
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