Why Can’t I Print In RGB?

Ever felt frustrated and confused when the colours you set in your digital files don’t match up when they are printed? Or when the printing company tells you that your file is in RGB and it is incompatible? Fret not; we are here to give you a quick rundown of why you can’t just print in RGB.

What is RGB and CMYK?



For a start, RGB stands for the primary light colours of Red, Green and Blue – viewed on the display screen. These colours work on an additive colour system. This means that the colours are added up and combined in various proportions to produce a range of colours. Because the RGB colour model uses an 8-bit format, the three colours are represented in integer values from 0 to 255. This results in 16777216 (256 x 256 x 256) possible colour combinations. For example, in a Photoshop file, a pure white colour is shown as (R: 255, G: 255, B: 255). The code indicates how all three RGB colours are fully and equally combined to produce the pure white colour.


CMYK_subtractive_color_mixing.svg copy


On the other hand, CMYK stands for Cyan, Magenta, Yellow and Key (Or Black) – viewed (in ink or dye) on print. CMYK works on a subtractive colour system instead. This is the reverse of RGB, meaning that the colours are taken away when they are mixed together. As each additional drop of ink diminishes the light that would otherwise be reflected, the mixing of dyes create darker shades of colours. CMYK is represented as percentages of ink added. For example, pure white colour is displayed as (C: 0%, M: 0%, Y: 0%, K: 0%), implying that no ink is added.  


When to Use RGB or CMYK?


As a general rule of thumb, RGB is used for screens, while CMYK is used for printed works.  If you even have the slightest inclination to print a piece of work, go for the CMYK system. 







Why Are There 2 Different Colour Systems?

The short answer is that you can’t print light. The display screen uses combinations of pixels to display colours, and these pixels emit light. When the screen is off, it remains black because no light is emitted.  On the flip side, we perceive the colour of ink and dyes on print due to the reflection of light. This means that the ink absorbs some colours while the rest is reflected off. When no ink is added, a standard white printer paper remains white (contrary to the black computer screen display).  Such differences have led to the creation of the RGB and CMYK systems.


Why should I care about these two colour systems?



RGB (Left) Vs CMYK (Right)


As the range of colours available in the RGB system is larger than the CMYK system, certain RGB colours cannot be replicated under the CMYK system. Such colours are referred as “out of gamut”. As such, if you send a file in RGB mode for printing, some printers (especially commercial ones) will not accept it. Other printers automatically convert RGB colours to CMYK alternatives, but the colours will turn out very different. Often times, the automated CMYK colours are duller and lack detail compared to their RGB counterparts. This is the reason why professional printing companies would rather ask you for a CMYK version. After all, you will have better control over the final appearance.


What should I do once I receive my artwork?


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There are a few steps that you should take. The first step is to ensure your files are in CMYK. If you are unsure, you can engage a professional designer or a printing company.  You can request them to alter the files into CMYK. Alternatively, you can use softwares from Adobe Creative Suite and search for tutorials found online if you want to change it yourself.

Do you have any more questions regarding RGB or CMYK colour modes? Feel free to ask them in the comments below! If you are curious to know about other design related issues, you can check out our article explaining what some common design mistakes that companies make.

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