Vision, the human visual system, is a complex interplay between various components of the eye, including the cornea, pupil, lens, iris, retina, and optic nerve. It collaborates to capture, focus, and convert light into electrical signals that are transmitted to the brain for visual processing and interpretation.

  • Vision begins when light emitted or reflected by an object or scene enters our eyes through the cornea, pupil, and lens.
  • The cornea and the lens work together to concentrate and focus light onto the retina, which is the photosensitive layer of cells at the back of the eyeball.
  • The iris, located between the cornea and the lens, regulates the amount of light reaching the retina. It also determines eye color and controls the size of the pupil.
  • The retina plays a vital role in converting differences in the wavelength and brightness of incoming light into electrical signals.
  • The optic nerve, which exits at the back of the eye, carries these signals to the visual processing areas of the brain.
  • Vision, as experienced by human beings, forms the foundation of visual perception.
  • Visual perception is the human ability to see and understand our surroundings by virtue of the sensitivity of our eyes to wavelengths of light across the entire visible spectrum, from red to violet.
  • Visual perception is linked to eyesight but also encompasses the brain’s capability to interpret and comprehend the information received from our eyes.
  • Visual perception is the outcome of visual processing, the complex and dynamic process that involves interactions between various retinal cells, neural pathways, and brain regions, ultimately leading to conscious visual perception.
About light, colour & vision
  • The human eye and human vision are adapted and responsive to the visible spectrum, which includes wavelengths of light corresponding to colours ranging from red to violet..
  • Light is the electromagnetic radiation that enables us to perceive colour. It consists of a spectrum of wavelengths, and it is the interaction of these wavelengths with our visual system that gives rise to the perception of different colours.
  • The visible spectrum is the range of wavelengths of light that the human eye can detect, typically spanning from approximately 400 nanometers (nm) for violet to 700 nm for red.
  • Light is seldom composed of a single wavelength, so an observer is typically exposed to a range of diverse wavelengths or a combination of wavelengths from various parts of the visible spectrum.
  • Visible light does not possess any properties that set it apart from other segments of the electromagnetic spectrum.
  • When light enters the eye, it interacts with specialized cells called cones in the retina. Cones are responsible for detecting and processing different wavelengths of light, which contribute to our perception of colour.
  • The three types of cones, commonly referred to as red, green, and blue cones, respond to different ranges of wavelengths. The combined activity of these cones allows us to perceive a wide range of colours.
  • The brain plays a crucial role in the perception of colour. It processes the signals received from the cones and interprets them to create our conscious experience of colour.
  • Colour perception is influenced by various factors, including the intensity and quality of light, the surrounding environment, and individual differences in vision.
  • Our ability to perceive and differentiate colours provides important cues about the world around us, helping us recognize objects, navigate our environment, and experience the richness of visual stimuli.
About trichromatic colour vision (Trichromacy)

Trichromatic colour theory explains how the human eye perceives colour.

  • Trichromatic colour theory is based on the existence of three types of light-sensitive cone cells in the retina, each responsive to a different range of colours.
  • The colours we perceive result from the combined responses of all three types of cones.
  • The sensitivity of cone cells forms the physiological basis for trichromatic colour vision in humans.
  • The ability to see colour stems from interactions among the three types of cones, with each cone exhibiting a preference for specific wavelengths within the visible spectrum.
  • The three cone types are denoted by the initials L (responsive to long wavelengths), M (responsive to medium wavelengths), and S (responsive to short wavelengths).
    • L-type cones exhibit the highest responsiveness to light with long wavelengths, favouring wavelengths around 560 nm.
    • M-type cones exhibit the highest responsiveness to light with medium wavelengths, favouring wavelengths around 530 nm.
    • S-type cones exhibit the highest responsiveness to light with short wavelengths, favouring wavelengths around 420 nm.