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What kind of colour perception do humans have?
Humans have trichromatic colour perception (blues, greens, and reds). Most mammals have a dichromatic view (blues and greens only), where snakes, rats, and mice have monochromatic views (no colours)
Describe the visual light spectrum?
Light is a wave, and each wave has a particular wavelength (cycle length) → we only see light on the visual portion of the electromagnetic spectrum (gamma, x-ray, ultraviolet, visible, infrared, microwave, radio/tv) which is approximately 400 THz to 700 THz. Most colours are a combination of multiple wavelengths (eg. white is a lot of every wavelength).
How does light enter our eyes to allow us to see colour?
Light is reflected off objects which enters our eyes and hits retinas, hitting cones (colour vision photoreceptors)
What are the three kinds of cones
L-cones (long wavelength cones) are maximally sensitive to red and yellows. M-cones (medium wavelength cones) are maximally sensitive to yellows and greens, and a little blue/cyan. S-cones (short wavelength cones) are maximally sensitive to cyans, blues, and violets
Based off the information received from the cones, a set of electrical signals is transmitted to the brain via the optic nerve informing colour vision.
What are the most common forms of colourblindness?
There are several kinds of colourblindness but the most common is red-green colourblindness (5-10% of men and 0.1% of females). This includes deuteranomaly (a weak perception of green, which is more common) and protanopia (no perception of red, which is second most common)
What causes colourblindness?
Colourblindness is usually inherited, and can be mild, moderate, or severe. Colourblindness occurs when one/more of the types of cone photoreceptors are absent, non-functional, or functioning ‘incorrectly’. Mild colourblindness is usually caused when all three types of cone are present, but one is not functioning ‘normally, where severe colourblindness is caused usually by the absence of multiple types of cone.
What is the value of motion detection?
It captures attention, it helps segment foreground from background, it helps compute distance to various objects in sight, helps computing the 3D shape of an object (important for optic flow), it allows for the estimation of the direction in which you are heading within the scene, it allows for recognition and prediction of actions
What is ‘looming’?
Detection of change in visual angle as you approach something/it approaches you → a nonlinear change, meaning that your reaction time is not a 1-1 ratio with distance
