RGB VS CMYK – What every Designer and Small Business Owner needs to Know!

RGB and CMYK – What’s the difference?

When getting the artwork ready for print there is one important thing to keep in mind: choosing the right colour spectrum. For this, there are two alternatives: RGB or CMYK. RGB is the colour spectrum used for images on screens only. CMYK, on the other hand, is the one used for printing. In other words, setting up the artwork in CMYK – also referred to as “four-colour printing” – is vital. An artwork set up in RGB may, in fact, cause colour variations and thus suboptimal outcomes.

The RGB colour spectrum and digital files

The term RGB stands for the three base colours red, green and blue. Together, these three colours build a spectrum serving as a reference value for all the various colour shades. Due to the different possible ratios, the RGB colour spectrum allows for wide range of different compositions – in fact, 16.8 million.

The RGB spectrum is an additive colour model meaning the more you add the brighter the colours become. To be more precise, setting all basic colours (RGB) to 100% results in pure white. Take the sun as an example: daylight is almost white, as the sun emits light in virtually all the visible wavelength spectrum. Traditionally, additive colours (RGB) are used for screens as such devices are emitting light, too. In other words, it makes sense to use a compatible structure for the picture and the device.

The CMYK colour spectrum and printed files

On the contrary, there is the subtractive (absorbing) colour scheme – CMYK. It consists of the four colours cyan, magenta and yellow and the key colour black. The key colour is required due to the fact that adding up cyan, magenta and yellow at 100% results in a dark brown – instead of a real black. Their main characteristic of subtractive colours is that the more colours you mix, the darker the result is. The reason for this is that in a subtractive colour scheme colours reflects the light. For this reason, black colours get hot quickly as they absorb light energy while almost reflecting none.

Ink and paint serve as an example here: light is being absorbed (or subtracted) – not emitted. For this reason, CMYK is used for offset printing – both at the small printer at home and the big printing machine at the copy shop – but also in online printing.

The process is as follows: The four single colours are subsequently printed on the paper – each with a specific ratio. In doing so all possible shades can be achieved. Theoretically speaking, more than 4 billion colour shades can be achieved using a CMYK colour spectrum. However, only a small portion of it can be displayed and printed. As a matter of fact, the CMYK colour spectrum is thus smaller than RGB.

Applying CMYK to the artwork

The tricky part is getting the artwork ready for print. Generally speaking, photos, pictures and other elements usually have an RGB format only and thus need to be converted into CMYK colours. This is a crucial requirement for printing.

However, simply converting RGB into CMYK is not as simple as it seems due to the fact that the same shade may not exist in both schemes. In this context, severe deviances can arise. For these reasons, Printulu recommends to set up the artwork properly using a CMYK color spectrum from the beginning. Nevertheless, pictures or other elements in RGB can be converted using a specific editing software. Yet, this process entails the risk of losing color data, which may cause deviations in color. Please note that only a calibrated screen can show potential deviations accurately.