Foundation
From light and spectra to cameras, displays and perception: what physically exists in a scene and why digital colour is a model rather than a copy of reality.
Colour is not stored inside an object as a ready-made property. A light source illuminates a material, the material reshapes the spectrum, the eye and brain interpret the result, and cameras and displays only build technical models of that process.
Quick reference
Colour perception starts with a spectral stimulus, not an RGB code.
The light spectrum and material reflectance/transmittance jointly form the stimulus.
Colour is produced by the visual system under defined viewing conditions.
A display reproduces a visual response rather than the object's original spectrum.
Physically, a source emits energy across wavelengths. Human vision responds only to a small region we call visible light. It is more useful to think in terms of spectral power distribution, or SPD, than a single number describing the 'colour of a lamp'. Two sources with similar correlated colour temperature can have very different SPDs and can render materials and cameras differently.
Monochromatic light can be associated with one wavelength, but most real colours are produced by mixtures of many wavelengths. Purple colours do not correspond to a single spectral wavelength at all; they arise from combinations of long- and short-wavelength energy. That is why the simple formula 'colour equals wavelength' is too crude for colour science.
An illuminant is a standardised or described spectral lighting condition. It determines which parts of the spectrum are available for an object to reflect in the first place. D50, D60 and D65 are not creative tint presets; they are reference illuminants and white-point conventions that later become part of colour systems and adaptation workflows.
A surface absorbs part of the incoming spectrum and reflects another part; transparent materials may also transmit light. Spectral reflectance is a physical property of the material, but the visible result changes with the illuminant. A red fabric under a source with little long-wavelength energy does not have to look conventionally red.
After light interacts with a material, a spectrum reaches the eye and the visual system converts it into a small set of receptor responses. The brain also uses surround, adaptation and relative brightness and colour relationships. In a strict sense, colour is therefore not just a physical spectrum but a perception produced for an observer under defined conditions.
If two different spectral distributions produce sufficiently similar tristimulus responses, an observer may perceive them as the same colour. These matches are called metamers. Colour reproduction fundamentally relies on this: a display does not reproduce the spectrum of a real object, but its RGB mixture can trigger a similar visual response.
A sensor uses its own spectral sensitivities and colour filters. The manufacturer then converts those responses into camera RGB, log encoding or RAW metadata. A camera therefore does not record 'absolute true colours'; it measures the scene through its own system and later relies on colour transforms, matrices and profiles.
A display mixes its own red, green and blue primaries. Their spectra are normally very different from those of the original object, but a correct colour pipeline makes them produce the required CIE tristimulus values and a convincing visual match. This is where RGB primaries, white point, gamut, transfer functions and colour spaces enter the story.
For post-production, keep one chain in mind: illuminant → spectral scene → camera response → encoded signal → working colour space → creative grade → output transform → display emission → observer. An error at any stage may look like 'wrong colour' even though the underlying cause is completely different.
When Resolve shows Rec.709, LogC4, D65 or CST, these are not unrelated magic settings. They describe different stages of one chain: how the camera represented the scene, the space you work in and how the result should become light on a particular display.
Technical definitions are anchored to standards bodies and primary specifications wherever that distinction matters.
