Human vision

The human visual system: the eye, retina, and brain pathways that turn light entering the pupil into perceived scenes, color, and motion.

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Photoreceptor cell: Retinal neuron that converts light into electrical signals: rods for dim light, cones for daylight and color. The transduction step where light first becomes a neural signal.
Electromagnetic spectrum: The full range of electromagnetic radiation; visible light is the narrow band from roughly 380 to 750 nm. Defines the physical stimulus vision is built to detect.
Color blindness: Deficient color discrimination, most commonly red-green, caused by missing or altered cone photopigments. Inherited cone defects expose how normal color vision is constructed.
David Hubel: Neurophysiologist who, with Torsten Wiesel, mapped receptive fields in visual cortex and shared the 1981 Nobel Prize. His single-cell recordings defined how cortical neurons encode edges and orientation.
Digital camera: Device converting light into digital images with a sensor of millions of photodiodes replacing film. Camera engineering parallels retinal transduction; both solve the same optical problems.
Rhodopsin: Light-sensitive pigment in rod cells; a G protein-coupled receptor whose isomerizing retinal triggers the visual cascade. The actual molecule that absorbs incoming photons and starts the signal.
Receptive field: The region of visual space and stimulus pattern that changes a neuron's firing rate. The organizing principle by which visual neurons encode the image.
Blindsight: Residual visual responses to stimuli in patients with damaged primary visual cortex who report seeing nothing. Shows which visual abilities can survive without conscious cortical vision.
Torsten Wiesel: Neuroscientist who co-discovered visual cortex organization and critical periods for ocular dominance with Hubel. Showed vision's cortical wiring depends on early visual experience.
Computer vision: Field of artificial intelligence enabling machines to extract meaning from images, now dominated by deep networks. Machine systems borrowed and tested ideas about hierarchical visual processing.