Color Science Quiz: Metamerism, CRI and Color Accuracy

Metamerism is when two colors that have different spectral makeups look identical under one light source but different under another. A fabric and a paint chip can match in daylight and clash under warm indoor bulbs.

Metamerism occurs when two color samples match under one light source but differ under another, because their spectral reflectances are different even though they stimulate the eye identically under the first source. Different retail and home lighting spectra reveal these underlying differences.

The Color Rendering Index rates how accurately a light source shows colors compared with a reference such as daylight, on a scale up to 100. Lights with a high CRI, around 90 or above, render skin and products more faithfully.

Many LEDs emit light in a few narrow bands rather than a smooth, continuous spectrum. Colors that fall into the gaps are poorly lit, and sensors may record them differently than the eye sees them, causing odd or muted colors.

The color filter array is a pattern of tiny red, green and blue filters over the sensor's pixels. Its exact filters determine how light of each wavelength is split into the camera's RGB channels, which shapes the camera's color rendering.

White balance shifts whole channels warmer, cooler, greener or more magenta, so it fixes overall color casts. It cannot add back wavelengths missing from a light's spectrum, so pigments that reflect mainly those wavelengths stay off.

A color checker is a chart of patches with precisely known color values. Photographing it under the shoot's light lets software build a camera profile that corrects the camera's color response, making colors accurate and consistent.

When source colors fit within the destination gamut, rendering intent makes no difference. Only when colors fall outside the destination can the choice of intent affect the result, making the decision most consequential in wide-to-narrow gamut conversions.

Fluorescent sources emit a non-continuous spectrum with a pronounced green spike. Correcting the overall color temperature to neutral is not enough; the residual green requires a compensating magenta tint adjustment to render skin tones accurately.

A camera profile characterizes how the sensor's specific spectral sensitivities translate to target color values. Changing the profile alters the color and tonal rendering of every image processed through it, independently of white balance or exposure settings.

Every color space has a boundary; colors that fall outside it have no equivalent in the destination. When a conversion encounters an out-of-gamut value, it must either clip it to the boundary or compress the surrounding gamut to fit, depending on the rendering intent chosen.

sRGB matches the gamut assumption built into web browsers and consumer displays. Embedding the sRGB profile ensures images render consistently across different screens without requiring color management software on the viewer's end.

D65 is a standard illuminant that represents average daylight, at a color temperature of about 6500 K. It serves as the white point of sRGB and a common reference for monitor calibration.

The tint slider adjusts the balance between green and magenta in a color cast correction. It works perpendicular to the warm-cool axis of the temperature slider, and is the primary tool for removing the green bias common in fluorescent and some artificial light sources.

Each sensor's silicon has its own spectral response curve, which determines how it weights different wavelengths. Two cameras with identical color temperature settings may still render a scene differently because their sensors respond unequally to the same light.