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Image editing, design, photography or printing. Two different colour models not only determine our daily work: RGB and CMYK. Knowing the differences and usage is important.

The RGB colour model

The RGB colour model is a additive colour model based on the three basic colours Red, Green and Blue. The colours are also called colours of light, because the additive colour model creates colours by mixing light.

Adding the three basic colours in different intensities results in different colours. The RGB value describes individual colour and defines the respective proportion of red, green and blue. Value 0 = no proportion of this basic colour. Value 255 = maximum proportion of this basic colour. The greater the proportion of the colours, the brighter the colour mixture. At the highest intensity, all three colours result in pure white (RGB 255, 255, 255). The absence of all three colours is black (RGB 0, 0, 0).

Theoretically, all visible colours can be displayed with the RGB model in this way. For technical reasons, a total of around 16.8 million different colour shades can be mixed in reality.

Usage

– Enables the display on a screen, e.g. TV, computer, camera, smartphone. Only three light sources for red, green and blue are required.

– Ideal for digital work, e.g. digital pictures, graphic design, web design, videos.

– The file formats JPEG, PNG, PSD and GIF are best suited.
More about the different image formats and vector formats in our blog.

Good to know

RGB is a device-depended colour model. Our Br24 dark blue, for example, has the RGB value 13, 0, 76. However, the display of this colour tone differs from device to device and depends, among other things, on the device’s internal colour settings.

The CMYK colour model

The CMYK colour model is a subtractive colour model based on the three basic colours Cyan, Magenta, Yellow and additionally Key (black). Key originates from the so-called key plate, a printing plate. Which already shows that the CMYK model is used in the field of printing. Ink absorbs light, which is why the model is called subtractive.

One after the other the basic colours are applied on a (usually) white background, which results in different colour shades depending on the mixing ratio. The more colours are used, the darker the colour tone. The CMYK value describes each individual colour and defines the respective percentage of cyan, magenta, yellow and key (black). The greater the proportion of the colours, the darker the colour mixture.

In theory, the mixture of 100% cyan, magenta and yellow results in the colour black. In reality, however, only a very dark brown grey arises. Therefore the key colour black is added when printing. This not only produces pure black, but the intensity of grey values and shadows can also be increased. Therefore, black does not equal black in printing. Depending on the ratio in which the three primary colours and the key colour are represented in black, the black appears different.

The CMYK model can theoretically represent more than 4 billion different colours. However, only significantly fewer colours can be displayed on a screen or generated during printing. Ultimately, CMYK comprises far fewer colours than RGB. For example, very bright colours must be printed with special colours. The colour white can only be achieved by the absence or omission of colours or with a special colour in the so-called white printing.

Usage

– CMYK is a prerequisite for four-colour printing and is used, for example, in offset printing (e.g. online printing industry).

– Creation of print data for printed projects, e.g. business cards, flyers, product packaging, printed T-shirts.

– The file formats PDF, AI and EPS are best suited.
More about the different image formats and vector formats in our blog.

Good to know

Photos and images are mostly in RGB. In order to integrate them into print data, they have to be converted into CMYK (colour separation). Since RGB can display significantly more colours than CMYK, it often comes to colour deviations, also called colour shifts. To ensure optimal and as realistic colours as possible, the image processing is therefore always done in RGB mode. The conversation to CMYK takes place afterwards with a copy of the image file. With the help of colour profiles and gamut mapping, it is possible to keep colour deviations to a minimum.

CONCLUSION

– Which colour model is best suited depends on the usage.

– The RGB colour model is ideal for digital work and screen display.

– The CMYK colour model is suitable for creating print data.

Colour profiles and gamut mapping? What this is exactly about and even more about colour models and colour spaces, you can find out in our blog “All about colour – Colour model, space, profile & gamut mapping”.