Spectral colour model

• • The spectral colour model is typically represented as a continuous strip, with red at one end (longest wavelength) and violet at the other (shortest wavelength).
  • Wavelengths and Colour Perception: In the spectral colour model, each wavelength corresponds to a distinct colour, ranging from red (with the longest wavelength, around 700 nanometres) to violet (with the shortest wavelength, around 400 nanometres). The human eye perceives these colours as pure because they are not the result of mixing other wavelengths.
  • Pure Colours: Spectral colours are considered “pure” because they are made up of only one wavelength. This is in contrast to colours produced by mixing light (like in the RGB colour model) or pigments (in the CMY model), where a combination of wavelengths leads to different colours.
  • Applications: The spectral colour model is useful in understanding natural light phenomena like rainbows, where each visible colour represents a different part of the light spectrum. It is also applied in fields like optics to describe how the eye responds to light in a precise, measurable way.

Spectral colour concepts

• • • It helps explain concepts such as:
    • The visible portion of the electromagnetic spectrum, which ranges from approximately 400 to 700 nanometres.
    • The relationship between wavelengths of light and how we perceive colour.
    • Natural phenomena like rainbows and other effects involving chromatic dispersion, where light is split into its component spectral colours.

Beyond spectral colour

• • • The spectral colour model helps us to understand the connection between the physics of light and the perception of colour but other models are needed to help to make sense of how the eye works and to manage colour in different practical situations:
    • The trichromatic colour model deals with the physiological aspects of colour.
    • CMY colour model deals with how coloured inks behave in the world of digital printing.
    • RGB colour model deals with the display and management of colour in digital environments.
    • HSB colour model provides an intuitive way to select and edit colours in digital workflows.

Spectral colour

• A spectral colour is a hue perceived by human vision when exposed to a single wavelength of visible light. In normal (trichromatic) vision, each wavelength evokes a distinct spectral colour, ranging from red to violet.
• The human eye is finely tuned to the visible spectrum, where each wavelength corresponds to the perception of a different spectral colour.
• A spectral colour is considered monochromatic, meaning it contains just one wavelength and produces a hue different from any other wavelength.
• All light sources, such as sunlight, artificial lights, lightning, candles, and even glow worms, emit a mix of wavelengths. Each individual wavelength within this mix corresponds to a specific spectral colour.
• The colours we perceive in the world arise from different combinations of wavelengths of light reflecting off surfaces and objects. When light reaches the light-sensitive cells in our eyes, this combination produces the colours we experience.
• While the Sun emits a broad range of wavelengths that include all the colours in the visible spectrum, an LED bulb might only emit light at a specific wavelength, corresponding to one spectral colour.
• Although we cannot distinguish all wavelengths individually, we see the full range of spectral colours when observing a rainbow or when light is dispersed through a prism.
• In everyday experience, what we perceive as a spectral colour often includes a narrow band of adjacent wavelengths.
• Spectral colours are sometimes referred to as pure hues or monochromatic hues because they consist of one wavelength, unblended with others.
• While sunlight traveling through the air appears invisible, if it strikes a neutral-coloured surface and all wavelengths are reflected equally, the light is perceived as white.
• Spectral colours are commonly represented as a continuous strip, with red at one end and violet at the other, illustrating the range of hues corresponding to different wavelengths.