Chromatic adaptation is the human visual system's ability to adjust to changes in illumination. When you move from daylight (bluish, ~6500K) to indoor tungsten light (warm, ~2856K), your eyes automatically "recalibrate" so that a white piece of paper still appears white. This tool uses the Bradford transform to mathematically model how any given color would be perceived under a different light source after your eyes have adapted.

The Bradford chromatic adaptation transform (CAT) is the most widely used mathematical model for predicting corresponding colors under different illuminants. It works by converting XYZ tristimulus values into LMS cone response space using an optimized 3×3 matrix, scaling the LMS values according to the white point shift, and converting back. It was developed by Lam and Rigg at the University of Bradford and is the default CAT in ICC color management systems.

Different light sources have different spectral power distributions (SPDs). Daylight (D65) has a relatively flat spectrum, while tungsten bulbs emit more energy in the red-orange region, and fluorescent lights have spikes at specific wavelengths. When light reflects off a colored surface, the reflected spectrum is the product of the light's SPD and the surface's reflectance. This means the same physical color can trigger different cone responses under different lighting — and your brain's chromatic adaptation mechanism partially (but not fully) compensates for this shift.

D65 (6500K) represents average northern hemisphere daylight and is the standard white point for sRGB, HDTV, and most digital displays. D50 (5000K) is the standard for the printing and graphic arts industry (ICC profiles use D50). Illuminant A (2856K) represents a typical household tungsten/incandescent bulb — much warmer with a strong orange-yellow cast. Each has different CIE XYZ white point coordinates, which drive the chromatic adaptation calculation.

Graphic designers often design on D65-calibrated monitors but need to preview how colors will appear in D50 print viewing booths. Photographers shooting under mixed lighting can better understand color shifts. Interior designers can predict how paint colors will look under different lighting. This tool gives you a scientifically-based preview before committing to expensive proofs or prints. It's also invaluable for understanding white balance and color management workflows.

Color temperature (measured in Kelvin) describes the spectral characteristics of a light source by comparing it to an ideal "black body radiator" heated to that temperature. A black body at 2856K glows with the warm orange-white of a tungsten bulb; at 6500K it matches daylight. The white point is the CIE XYZ coordinate corresponding to that color temperature. For the daylight locus (D series illuminants, 4000K+), the coordinates follow a specific curve in chromaticity space that slightly differs from the pure black body (Planckian) locus.

When chromatic adaptation shifts a color's XYZ values significantly, the resulting sRGB values may fall outside the 0–255 range (or 0–1 in linear terms). This means the "corresponding color" cannot be accurately displayed on a standard sRGB monitor — it's "out of gamut." In this tool, such values are clipped to the nearest valid boundary, and a warning icon (⚠) appears on the affected swatch. In professional color management, more sophisticated gamut mapping algorithms (like perceptual or relative colorimetric intent) handle these cases.

The Bradford CAT is considered the most accurate general-purpose chromatic adaptation model for reflected surface colors, which is why it's the default in ICC v4 color management. However, it's not perfect — especially for highly saturated colors, fluorescent materials, or extreme illuminant shifts. Other models like CIECAT02 (from CIECAM02), von Kries, and Sharp exist, each with slightly different LMS cone response matrices. For most practical applications in photography, design, and print, Bradford provides excellent results.

White balance correction in photography is essentially an application of chromatic adaptation. When you set your camera's white balance from "Tungsten" to "Daylight," the camera applies a gain adjustment to the red, green, and blue channels — similar to scaling in LMS space. However, camera sensors don't perfectly match human cone responses, so real-world white balance is more complex. This tool shows the theoretical perceptual result, which is what good white balance aims to approximate.

F2 (4230K) represents a "cool white" fluorescent lamp — common in older office and retail lighting. F11 (4000K) is a TL84 narrow-band triphosphor fluorescent — widely used in European retail environments. Unlike black body radiators or daylight, fluorescent lights have irregular spectral power distributions with sharp peaks, which can cause some colors to appear dull or shifted in ways that chromatic adaptation alone cannot fully predict. The CRI (Color Rendering Index) of F2 is about 64, while F11 is about 80 — neither is ideal for color-critical work.