Colour Gamut: What is it?
In order to better understand colours, you need to know what a colour gamut is. Basically, a color gamut refers to the range of colours that can be accurately represented by a device such as monitors and printers. It is the colours that the output device can produce. Devices with a larger gamut, such as monitors, can produce much more colours than devices with a smaller gamut, such as printers. Each device will have it's own unique colour gamut and as such represents colors slightly (or even dramatically) different.
RGB (Red, Green, Blue): The colours of light
Think of it like this:
Key characteristics of RGB
CMYK (Cyan, Magenta, Yellow, Key/Black): The Colours of Pigment
CMYK is a subtractive color model. This means that colors are created by subtracting (absorbing) light. When light hits an object, certain wavelengths are absorbed by the pigments and others are reflected. The reflected wavelengths are what we perceive as color. In CMYK, the inks absorb different parts of the visible spectrum.
Why "K" for black?
While theoretically combining 100% cyan, magenta and yellow ink should produce black, in practice, it often results in a muddy brown. This is due to impurities in the inks. Therefore, a separate black (Key) ink is added to achieve true blacks, provide richer shadows, and reduce the amount of coloured ink needed for darker tones, which saves costs and allows for finer details.
Think of it like this:
Key characteristics of CMYK
When to use which
The choice between RGB and CMYK is determined by your final output
For anything that will be displayed on a screen
For outputs such as websites, digital art, social media graphics, videos etc, use RGB. Designing in CMYK for screen display will result in duller, less vibrant colours
For anything that will be printed
Brochures, business cards, posters, t-shirts, documents etc. should be designed using CMYK. Designing in RGB for print outputs can lead to unexpected color shifts and less accurate representation of your vision once printed. Printers simply cannot reproduce the full spectrum of RGB colors.
The conversion challenge
Converting between RGB and CMYK is not always straightforward. When you convert an RGB image to CMYK, some colours that exist in the RGB gamut (like very bright greens or blues) may not be reproducible in CMYK. This is known as "out-of-gamut" colors, and they will be shifted to the closest CMYK color in the gamut. This will result in a noticeable color shift, and may even produce a completely different color.
Tips for a smoother workflow
Start in the correct color mode
If you know your final output will be print, it's often best to design directly in CMYK from the beginning, or at least be aware of potential color shifts.
Soft proofing
Many design software programs offer a "soft proofing" feature that simulates how your RGB design will look when converting to CMYK. This allows you to make adjustments before printing.
Use pantone colors for critical branding
If color accuracy is paramount for your brand (e.g., a specific logo colour), consider using Pantone (spot) colors, which are pre-mixed inks that offer consistent color reproduction across different printing methods.
In conclusion
Understanding the fundamental differences between RGB and CMYK is essential for achieving accurate and vibrant colours in all your visual projects, whether they live on a screen or in print. By choosing the right color model for the right application, you can ensure your colors always look their best.