15/10/2024

RGB to CMYK: two printed test sheets with comic designs compared

RGB to CMYK: why colours look different in print

Updated on 14 September 2026

Have you ever had a nasty surprise and wondered: ‘That is not the colour I had in mind. How did that happen?’ Then you have come to the right place. On screen your design glows, but on the finished transfer it looks duller or darker. This is almost always down to the colour space. In this article, we explain the difference between RGB and CMYK, show you what our colour test revealed and how to set up your file so that the colours in print are as accurate as possible.

RGB and CMYK: light versus ink

RGB is the colour space of screens. Monitors, smartphones and cameras mix their colours from red, green and blue light. The more light, the brighter the colour. This creates very vivid tones.

CMYK is the colour space of printing. Printing uses cyan, magenta, yellow and black. The ink sits on the material and absorbs light instead of glowing itself. That is why the CMYK colour space is smaller: some colours that a screen can show cannot be achieved with ink.

Particularly affected are bright greens, blues, oranges and pinks. They become duller in print.
On screen, colours always look a little brighter and more radiant than on the finished transfer, because the screen itself emits light.
When converting from RGB to CMYK, colours outside the print colour space are shifted to the nearest printable colour. If this only happens during printing, you no longer have any control over it.

In DTF printing, white is added as a separate colour. It is printed behind the colours so that they stay strong on dark textiles too. Set up white areas in your design as CMYK 0/0/0/0. Sublimation and UV DTF Transparent do not print white. There, the surface shows through and affects the colour, which is why the colours look best on light surfaces.

Our colour test: one design, four files

We wanted to see for ourselves how big the difference is in practice. So we printed the same design in four versions and compared the prints: twice in CMYK, once with DeviceCMYK and once with ISO Coated v2 (ECI), plus the same file in RGB, once as a PDF and once as a PNG. The result:

CMYK with DeviceCMYK or ISO Coated v2 (ECI): hardly any difference, the colours came out as they were set up.
RGB as a PDF: only slight deviations.
RGB as a PNG: clear colour deviations.

The reason: a PNG file only knows RGB. For printing, it is always converted to CMYK, and this may not produce the colour you had in mind. So it is best to save your print files as a PDF in CMYK. You can read more about this in the article PDF and PNG files compared.

How to set up your file correctly

Plan the colour space from the start. If you only switch from RGB to CMYK at the end, you will already get the surprise on screen and have to rework your design.

Set up your file in the CMYK colour space from the start.
Use the colour profile ISO Coated v2 (ECI), for sublimation ISO Coated v2 300 %. We show you how to set it up in How do I install an ICC profile?
Set up white as CMYK 0/0/0/0 and black as CMYK 0/0/0/100, not 400 per cent black.
Avoid spot colours such as Pantone or HKS, as they lead to colour deviations.
We cannot print gold, silver and neon, as we print exclusively in CMYK. Such tones can only be imitated with CMYK, without any shine or luminosity.
Save as a PDF. A PNG only knows RGB and is always converted to CMYK for printing. PNG files can also cause white flashes, i.e. fine white edges along the outlines.

Photos from your phone, images from the internet and many online tools work in RGB. In Canva, you will find the ‘CMYK’ colour profile setting when downloading a PDF for print, provided your account offers it.

Already have an RGB file? Then convert it yourself before uploading it. In Photoshop, you do this via Edit > Convert to Profile with ISO Coated v2 (ECI). Then check the colours and adjust them where they have become dull. This way, you decide how the colour looks, not the conversion during printing.

We do not change any colours in your file, we print what you set up. You can find all requirements at a glance under Setting up print files correctly.

Check colours before printing

Every screen shows colours slightly differently. Screen type, brightness, factory settings and features such as night mode change how colours are displayed. The same design therefore looks different on a phone than on a laptop or an office monitor. No screen shows you reliably what your print will look like. But these tools will get you close:

Colour proof: In Photoshop and Illustrator, choose Working CMYK under View > Proof Setup. Use View > Proof Colours to switch the print preview on and off. This preview is only reliable on a calibrated screen, otherwise it gives you a rough idea.
Gamut warning: In Photoshop, View > Gamut Warning highlights all areas that cannot be printed in CMYK. It also works without a calibrated screen, because it checks the colour values in your file, not the display.
Calibrate your screen: With a screen calibration device, your screen shows colours and the colour proof much more accurately.
Screen brightness: Do not set your screen to full brightness. Otherwise every colour will look more radiant than it will be in print.

Only a real print is truly reliable, and that is exactly what our colour chart is for.

Play it safe with the colour chart

If a colour has to be exactly right, for example for a company logo, do not take it from the screen. Our colour charts are real printed transfers with 964 colour swatches, each labelled with its CMYK value. They are printed with the ISO Coated v2 (ECI) colour profile that we recommend above. Pick the right swatch and enter its value in your file. If you keep these settings, your print will come out exactly in the colour of the swatch. This is also the easiest way to match Pantone or HKS specifications from a style guide. A small colour chart is also included in the Sample Pack, together with test prints of our products.

View DTF colour chart View UV DTF colour chart View Sample Pack

Questions about your file? Write to us via our contact form, we will be happy to help.

Also useful: Setting up print files correctly.

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