Colour Perception

Graphic and 3-dimensional interpretations of light in physical space

Prithvi Rana Dev · 2015

Note

Colour Perception investigates how light and hue shape our experience of structure. Through both sculptural and digital experiments — among them a hand-milled acrylic cone whose form follows the shape of the retina’s photoreceptors — I study how the splitting of white light, subsurface scattering, and wavelength-dependent reflectance can give cues to depth, curvature, and spatiality.

The series begins by following visible light through the forms we use to hold it. A prism opens white light into the linear spectrum; a wave gives each colour its length; the line is bent into a circle, and the circle revolved into a sphere — before the whole progression is lathed into a single object: an acrylic cone whose painted spectrum, viewed down its own axis, returns as concentric rings of colour. From there it turns to the eye itself, and to the range of colour vision found across other species — from our own three receptors to the sixteen of the mantis shrimp.

Digital — Adobe Illustrator · Sculpture — a hand-milled, drilled, lathed, and painted acrylic cone · Dimensions: 2.5 × 2.5 × 4 in

Digital illustration of a glass prism on a dark grey ground: a thin white ray enters from the left and leaves the far face as a band of seven colours, with the letters V, I, B, G, Y, O, R climbing the prism's near face in their own hues. — Plate I Dispersion: white light enters the prism and leaves as VIBGYOR — violet, indigo, blue, green, yellow, orange, red — each wavelength bent by its own measure.

Digital illustration on a dark grey ground: a circle drawn from many thin concentric rings, warm colours running up its left half and cool colours down its right, the remaining rings white, with a single vertical white line passing through the circle's seam. — Plate II The spectrum bent into a ring: warm wavelengths climb one side and cool wavelengths the other, set among rings of white — the two ends of the visible band brought around to meet at a single white meridian.

Digital illustration on a dark grey ground: a single wave travelling across a faint circle, its humps tightly spaced and violet at the left, lengthening through blue, green, yellow, orange and red, and fading to broad grey swells at either end. — Plate III Light is a self-sustaining wave: a changing electric field induces a magnetic field, which induces an electric field, ad infinitum — a physical line of force propagating through empty space at a constant 299,792 kilometres a second, the speed of light. Colour is simply its wavelength, lengthening here from the short violet end to the long red, with ultraviolet and infrared continuing in grey beyond either edge of what the eye can register.

Digital rendering of a translucent sphere on a dark grey ground, built from dozens of overlapping spectral rings revolved about a common axis, their faint tints summing toward white, with a small blue-violet point near the centre. — Plate IV The circle revolved: rings of every hue spun about a common axis overlap into a translucent sphere — colour given a third dimension, summing toward white.

Photograph looking straight down the axis of the acrylic cone: the painted spectrum reads as concentric rings, red and orange at the rim passing through yellow, green and blue to deep violet, around a white centre with a small dark core. — Plate V Down the axis of the cone, the painted bands collapse into concentric rings — red at the rim through to violet at the centre — the colour wheel re-emerging from a physical object. The cone is a three-dimensional figure of light, and a deliberate echo of the cone cells of the retina, the photoreceptors on which our colour perception depends.

Photograph of the sculpture: a small translucent acrylic cone resting on a white ground, its flare wrapped in spectral bands from a violet-blue throat to a red mouth, with a disc of red set into the centre of its face. — Plate VI The cone itself: hand-milled, drilled, lathed, and painted acrylic — the spectrum wound around its flare from the violet throat to the red mouth, a disc of red set at its axis. Its shape is drawn from the retina’s cone cells — the form of the receptor made large enough to hold in the hand.

Chromacy across species

If colour is assembled by the eye, then every kind of eye assembles a different colour. The number of distinct photoreceptor types an animal carries sets the dimensions of the colour space it can perceive — and that number varies widely across species. Each diagram below wraps its subject in one band of the spectrum for every class of receptor it sees by; the rings multiply as the eye grows richer.

Diagram on a dark grey ground: a walking human silhouette ringed by three bands of spectral colour, with three dots below in red, green and blue. — Trichromat Humans see by three cone types — sensitive to red, green, and blue — whose overlapping responses span the visible spectrum and let us distinguish roughly a million colours.

Diagram on a dark grey ground: a perched bird silhouette ringed by four bands, with four dots below including grey for ultraviolet. — Tetrachromat Most birds carry a fourth cone, extending their vision into the ultraviolet — revealing plumage patterns and markings that are wholly invisible to us.

Diagram on a dark grey ground: a butterfly silhouette ringed by five bands, with five dots below including grey and white. — Pentachromat Some butterflies have five or more receptor classes, reaching further into the ultraviolet still — tuned to read the markings of flowers and of one another.

Diagram on a dark grey ground: a mantis shrimp silhouette ringed by many bands, with sixteen dots below in a wide range of hues. — Dodecachromat The mantis shrimp carries up to sixteen kinds of photoreceptor — reading not only a broad multispectral range from ultraviolet to far red, but the polarisation of light itself, a dimension of vision we have no access to at all.

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