Colour Theory
What is colour? And why is it so difficult to judge? Well in a nutshell colour is the interpretation fabricated in our brain of a perceived frequency.
Colour does not exist.
Light
Inks
Substractive and Additive colour models
The subtractive colour model, also known as the CMYK colour model, is a method of colour reproduction that describes how colours are created in the physical world, particularly in the printing process. In the subtractive colour model, colours are created by subtracting wavelengths of light from white (or a light source) using colorants or pigments.
Here's how the subtractive colour model works:
Primary Colors:
In the subtractive colour model, the primary colours are cyan, magenta, and yellow (CMY). These colours are used as the base colours for creating other colours.
Each primary colour absorbs one of the additive primary colours (red, green, and blue) while reflecting the other two.
Secondary Colors:
By combining two of the primary colours, secondary colours are created. These are:
Red is created by mixing magenta and yellow.
Green is created by mixing cyan and yellow.
Blue is created by mixing cyan and magenta.
Tertiary Colors:
Tertiary colours are formed by mixing a primary colour with a neighbouring secondary colour. (see colour wheel).
Black:
In theory, the combination of cyan, magenta, and yellow should produce black. However, in practice, a small amount of black ink (also known as the "key" colour) is added to improve the depth and richness of shadows and to adjust colour balance.
The "K" in CMYK stands for "key," which represents the black channel in colour printing.
White:
Unlike in the additive colour model (RGB), where adding all colours together produces white light, in the subtractive colour model, combining all colours together (cyan, magenta, yellow, and black) results in a dark colour close to black, not white. This is because the pigments absorb light rather than emit it.
The subtractive colour model is used primarily in printing, such as in offset printing, digital printing, and colour photography. It's important to note that the subtractive colour model is different from the additive colour model (RGB), which describes how colours are produced by adding different wavelengths of light together.
In printing, CMYK colours are called process colours. Generally additional direct inks are added (spot colours) for practical reasons or to reach colours outside of the CMYK colour space (gamut).
The definition of colour
Colour is the visual perceptual property corresponding in humans to the categories called red, blue, yellow, etc. Colour derives from the spectrum of light (distribution of light power versus wavelength) interacting in the eye (specifically cones) with the spectral sensitivities of the light receptors. Colour categories and physical specifications of colour are also associated with objects or materials based on their physical properties such as light absorption, reflection, or emission spectra.
The colour wheel
The colour wheel is a circular chart that organises colours in a structured and visually intuitive manner based on their relationships to one another. It is a fundamental tool used in art, design, and colour theory to understand colour relationships, create colour schemes, and make informed colour choices. The colour wheel typically consists of primary, secondary, and tertiary colours arranged in a circular format. Here's a breakdown of its key components:
Primary Colours: The primary colours are the building blocks of the colour wheel and cannot be created by mixing other colours together. In traditional colour theory, the primary colours are red, blue, and yellow. These colours are evenly spaced around the colour wheel, forming equidistant points.
Secondary Colors: Secondary colours are created by mixing equal parts of two primary colours together. The secondary colours are located halfway between the primary colours they are created from. The three secondary colours are:
Green (created by mixing blue and yellow)
Orange (created by mixing red and yellow)
Purple (created by mixing red and blue)
Tertiary Colours: Tertiary colours are further combinations of primary and secondary colours. They are created by mixing unequal parts of adjacent primary and secondary colours. Tertiary colours are located between the primary and secondary colours they are mixed from. Examples of tertiary colours include red-orange, yellow-green, blue-purple, etc.
Complementary Colours: Complementary colours are located directly opposite each other on the colour wheel. When placed next to each other, complementary colours create strong visual contrast and can intensify each other's hue. Examples of complementary pairs include red and green, blue and orange, and yellow and purple.
Analogous Colours: Analogous colours are located adjacent to each other on the colour wheel. These colours share similar undertones and create harmonious colour schemes when used together. For example, blue-green, green, and yellow-green are analogous colours.
Split-Complementary Colours: Split-complementary colours are a variation of complementary colours. Instead of choosing one complementary colour, split-complementary colours use the two colours adjacent to the complementary colour. This creates a colour scheme with strong contrast and visual interest while maintaining harmony.
Triadic Colors: Triadic colours are evenly spaced around the colour wheel, forming an equilateral triangle. This colour scheme consists of three colours that are equally distant from each other, creating a balanced and vibrant palette.
The colour wheel serves as a valuable reference tool for artists, designers, and anyone working with colour. It provides a visual representation of colour relationships and helps in creating harmonious colour schemes, understanding colour mixing, and making informed colour choices in various creative endeavours.
the colour wheel is a 2 dimensional representation that can be moved on its "z" axis at any level of brightness or darkness (Lab model). In printing we will use a 3 dimensional representation called colour space (or gamut). Each print process is limited in its gamut, requiring the printing industry to implement spot colours, to widen the colour space available.
The colour space (gamut)
In the context of colour reproduction, colour management, and digital imaging, the term "gamut" refers to the entire range of colours that a device, such as a display or a printer, can reproduce or capture. It represents the spectrum of colours that are achievable within a particular colour space or system.
Here's a breakdown of the concept of gamut:
Colour Space: A colour space defines a specific range of colours using mathematical models. Common colour spaces include RGB (Red, Green, Blue) for digital displays and CMYK (Cyan, Magenta, Yellow, Black) for printing. Each colour space has its own gamut, which represents the subset of colours it can produce or reproduce.
Visible Spectrum: The gamut of human vision encompasses a vast range of colours visible to the human eye. However, no device can reproduce all the colours in the visible spectrum. Instead, devices are limited to reproducing a smaller subset of colours within this spectrum.
Device Gamut: The gamut of a device, such as a monitor or a printer, is determined by its colour capabilities, including its colour primaries (e.g., the specific shades of red, green, and blue for an RGB display) and its ability to reproduce different levels of saturation and brightness.
Colour Profiles: Colour profiles, such as ICC profiles, are used to characterise the colour capabilities of devices and define their gamut within a specific colour space. These profiles help ensure consistent colour reproduction across different devices by mapping colours from one device's gamut to another's.
Out-of-Gamut Colours: Colours that fall outside the gamut of a particular device cannot be accurately reproduced by that device. When working with digital images or designs, it's important to be aware of out-of-gamut colours and how they may be affected when transferred to different devices or colour spaces.
Understanding the gamut of a device is crucial for achieving accurate and consistent colour reproduction in digital or conventional imaging and printing workflows. By working within the gamut of a target device and using appropriate colour management techniques, it's possible to maintain colour fidelity and ensure that colours appear as intended across different devices and media. Generally a Spectrophotometer is used to measure on a physical substrate the difference between a colour and its target, the result is a "Delta E" being the gap from colour A to B.
Colours technical appellations
Technical colour names are specific and standardised terms used in various fields, including colour science, graphic design, printing, and digital imaging. These names often correspond to specific colour values defined within colour models such as RGB (Red, Green, Blue), CMYK (Cyan, Magenta, Yellow, Black), or LAB (CIELAB).
Here are some examples of technical colour names:
RGB Values: In the RGB colour model used for digital displays and web design, colours are defined by their red, green, and blue component values. For example, "RGB(255, 0, 0)" represents pure red, while "RGB(0, 255, 0)" represents pure green.
Hexadecimal Codes: Hexadecimal codes are commonly used to represent colours in web design and digital graphics. Each colour is represented by a six-digit code that corresponds to its RGB values. For example, "#FF0000" represents pure red, while "#00FF00" represents pure green.
CMYK Values: In the CMYK colour model used for printing, colours are defined by their cyan, magenta, yellow, and black component values. For example, "C:0 M:100 Y:100 K:0" represents pure red, while "C:100 M:0 Y:100 K:0" represents pure green.
LAB Values: The LAB colour space is a device-independent colour model used to represent colours based on human perception. Colors in the LAB colour space are defined by their lightness (L) and chromaticity coordinates (A and B). For example, "LAB(50, 0, 0)" represents a neutral gray colour.
Pantone Matching System (PMS): Pantone colours are standardised colours used in various industries, particularly in printing and branding. Each Pantone colour is assigned a unique name and code, such as "PANTONE 185 C" for a specific shade of red.
RAL Colour System: The RAL colour system is a colour standard widely used in Europe, particularly in architecture, construction, and industrial design. RAL colours are assigned numeric codes, such as "RAL 5002" for a specific shade of blue.
NCS (Natural Colour System): The NCS is a colour system based on the perception of colour by the human eye. NCS colours are defined using numeric codes and notation, such as "NCS S 1080-B90G" for a specific shade of green.
These technical colour names provide precise and standardised ways to specify and communicate about colours in various applications, ensuring consistency and accuracy in colour reproduction across different devices and workflows.
The importance of Colour Management in the print industry
Colour management plays a crucial role in the printing industry for several reasons:
Consistent Colour Reproduction: Colour management ensures that colours are reproduced accurately and consistently across different printing devices, substrates, and printing processes. This consistency is essential for maintaining brand identity, meeting customer expectations, and ensuring the quality of printed materials.
Brand Integrity: Many brands have specific brand colours that are integral to their identity and recognition. Colour management ensures that these brand colours are reproduced faithfully in all printed materials, helping to maintain brand consistency and integrity.
Customer Satisfaction: Consistent colour reproduction enhances customer satisfaction by ensuring that printed materials match their expectations and requirements. Whether it's packaging, marketing collateral, or product labels, accurate colour reproduction contributes to a positive customer experience.
Reduced Waste and Rework: Effective colour management reduces the need for reprints and colour corrections, minimising material waste and production costs. By achieving accurate colours on the first print run, printers can improve efficiency and profitability.
Workflow Efficiency: Colour management streamlines the printing workflow by providing standardised processes for colour calibration, profiling, and proofing. This consistency helps printers identify and resolve colour issues more efficiently, reducing production time and improving overall workflow efficiency.
Compliance with Industry Standards: Many industries have specific colour standards and requirements that must be met for regulatory compliance or to ensure compatibility with other systems and processes. Colour management helps printers adhere to these standards and produce output that meets industry requirements.
Cross-Media Consistency: Colour management ensures consistency across different media types, including print, web, and digital displays. By aligning colour output across various platforms, printers can maintain a cohesive brand image and messaging across all channels.
Improved Collaboration: Effective colour management facilitates collaboration between designers, prepress, printers, and clients by providing a common language for discussing colour and ensuring that everyone involved in the printing process has a shared understanding of colour expectations, and everyone understand the technical limitations of each process.
Overall, colour management is essential in the printing industry for achieving accurate, consistent, and high-quality colour reproduction, which is critical for meeting customer needs, maintaining brand integrity, and ensuring the efficiency and profitability of printing operations.