The CMYK (Cyan, Magenta, Yellow, Key/Black) and RGB (Red, Green, Blue) colour models are essential tools in the world of design, printing and digital media, but they are tailored for very different uses and are based on different underlying principles. Let’s compare their purpose, technical foundation, colour reproduction capabilities and usage in various fields.
The CMYK (Cyan, Magenta, Yellow, Key/Black) Colour Model
CMYK was specifically developed for printed materials. Whether you’re printing a book, poster, brochure, business card, or magazine, the CMYK model is used by printers to mix inks in order to reproduce colours on paper.
CMYK is a subtractive colour model, meaning that colours are produced by subtracting light. The model starts with white (typically the colour of paper) and uses the application of coloured ink to subtract certain wavelengths of light, resulting in the perception of various colours.
How it works:
- Cyan ink absorbs red light and reflects green and blue light
- Magenta absorbs green light and reflects red and blue light
- Yellow absorbs blue light and reflects red and green light
So by mixing these ink colours, other colours are created. Black (Key) is added to the CMY mix because combining all three colours doesn’t produce a deep enough black. It also helps define depth, contrast and shadows in printed images.
CMYK works by applying inks that subtract brightness from white light reflected off paper – and the more ink you add, the darker the colour becomes. A complete lack of ink results in white (the colour of the paper) and full coverage of ink results in black.
Compared to RGB, the CMYK model has a smaller colour gamut, meaning it cannot reproduce as many colours as RGB. This is why certain colours, particularly vibrant hues like reds, neon greens, blues and some purples, can appear dull or muted when printed.
CMYK cannot reproduce highly saturated and bright colours like RGB can and often results in colours that look slightly different in print versus on screen, which is why designers need to adjust their designs for print output.
Common issues in conversion from RGB to CMYK:
- Bright blues turn more purple or muted
- Vivid greens or pinks may lose their saturation
- Overall, colours can appear darker or more muted in print than on screen
Uses:
- Offset printing (commercial printing presses, such as for books, magazines, or large-scale printed media)
- Home and office printers (most colour inkjet and laser printers used at home or in the office use CMYK cartridges to print documents and photos)
In CMYK, colours are represented as percentages of the four inks:
- (0/100/0/0) represents pure magenta
- (100/0/0/0) represents pure cyan
- (0/0/100/0%) represents pure yellow
A combination like (0/100/100/0) produces red, since it uses equal amounts of magenta and yellow.
The RGB (Red, Green, Blue) Colour Model
RGB is used for digital displays, including screens such as TVs, computer monitors, smartphones, projectors, and any electronic device that emits light. Its primary application is in web design, digital art, video production and multimedia presentations.
RGB is an additive colour model, which means that it creates colour by adding light. In this model, the primary colours of red, green and blue are combined in varying intensities to create a wide spectrum of colours. Since it starts with black (the absence of light), when the maximum amount of red, green, and blue light is combined, it produces white. Conversely, when no light is emitted, pure black is created.
As an additive colour model, RGB relies on the direct emission of light. Colours are formed by increasing the intensity of the three primary colours, and the more light that’s added, the brighter and more vivid the resulting colour.
RGB is capable of producing an extremely broad range of colours – particularly in the bright and vibrant end of the spectrum – due to the nature of light, This is why RGB is ideal for use in digital screens, where light is directly emitted, allowing for vivid, saturated and intense hues that cannot be replicated by printed ink.
For example, RGB can display:
- Neon or fluorescent colours
- Bright blues and greens that are difficult to print accurately
- High contrast and luminous hues like bright pinks or bright purples
Uses:
- Web design (websites, user interfaces and mobile apps rely on the RGB model since they are viewed on screens)
- Digital art & photography (graphic designers and digital artists work in RGB to ensure that their work appears correctly on digital platforms)
- Video production (all forms of video, whether for online streaming or television, use RGB to represent colours, as the output medium is a screen)
In the RGB model, colours are represented as a mix of the three primary colours and are typically measured in values from 0 to 255 (representing intensity), with 0/0/0 being black and 255/255/255 being white. For example:
- (255/0/0) represents pure red
- (0/255/0) represents pure green
- (0/0/255) represents pure blue
Combinations of these values can produce millions of distinct colours.
The Key Differences Between CMYK & RGB
Medium
- CMYK is used for printing, where light is reflected off paper
- RGB is used for screens and digital displays, where light is emitted
Colour Creation
- CMYK uses a subtractive process (subtracting light) by layering ink to create colours
- RGB uses an additive process (adding light) to create colours
Colour Range
- CMYK has a smaller colour range, making certain vivid colours less achievable in print
- RGB offers a broader colour gamut, producing brighter and more vibrant colours
Brightness & Vividness
- CMYK colours often appear duller and less saturated due to the nature of ink and paper
- RGB can achieve intense, luminous colours, especially when viewed on backlit screens
Conversion
When converting from digital (RGB) to print (CMYK), certain colours may shift or appear dull, and designers must be mindful of this when preparing files for printing. This is a crucial step in ensuring the desired outcome on physical materials.
Designs for projects that will be printed (eg flyers, posters and brochures) should be created in CMYK colour spaces to better control the final printed colours.
When to Use CMYK or RGB
Use CMYK for printed materials, like posters, business cards, brochures and packaging. It’s important to adjust colours and design for the CMYK colour space to ensure accurate reproduction in print.
Use RGB for any design that will appear on digital screens, such as websites, apps, digital banners and online images.
In summary, CMYK is necessary for accurate printed results, while RGB is best for vibrant, screen-based designs. Understanding the differences and knowing when to use each model is key to achieving the best outcome in any design project.
