Colour perception

Importance of Colour Perception

Colour is used for aesthetics, signalling, and recognizing objects, as well as indicating social and cultural groups.

Source of Colour

Colour originates from visible light on the electromagnetic spectrum, with varying wavelengths corresponding to different colours.

Cone Photoreceptors

Humans have three types of cones (S, M, L) sensitive to blue, green, and red light, respectively.

Retinal Cone Mosaic

The distribution of cone types across the retina enables the ability to perceive colour.

Evolution of Cone Types

Dichromatic vision evolved 30-40 million years ago, followed by trichromatic vision for better colour discrimination.

Colour Vision Deficiency

Monochromats have one or no cone types, while dichromats lack specific cones (Protanopia, Deuteranopia, Tritanopia).

Anomalous Trichromats

Individuals with shifted cone sensitivities (Deuteranomaly, Protanomaly) experience altered colour perception.

Prevalence of Colour Deficiency

Colour vision deficiencies are more common in men due to X-linked inheritance (8% of men,

Cone Opponency

Signals from cones are combined into three opponent channels:L/(L+M), S/(L+M), and L+M.

Retinal Ganglion Cells

Opponent channels correspond to specific cell types in the lateral geniculate nucleus (LGN).

Memory Colour

Our perception of objects is influenced by typical colours, even when presented in grayscale.

Colour Constancy

The brain adjusts perceived colour based on lighting conditions, affecting how surfaces are perceived.

#THEDRESS Phenomenon

Differences in colour perception can be attributed to assumptions about illumination and colour constancy mechanisms.

Aesthetic Preferences

Colour preferences are influenced by positive or negative associations with objects of that colour (Ecological Valence Theory).

Colour Patterns

Natural scenes often dominated by blue-yellow variations align with aesthetic preferences.

Electromagnetic Spectrum

A diagram illustrating how varying wavelengths correspond to different colours.

Cone Types and Response Curves

Graphs depicting the response of S, M, and L cones to different wavelengths.

Retinal Cone Mosaic

An illustration showing the distribution of cones in the human retina.

Opponent Channels

Diagrams explaining the combination of cone outputs into L/(L+M), S/(L+M), and L+M channels.