CAM16 and Hellwig–Fairchild calculator
Compare what standard CAM16 and the 2022 Hellwig–Fairchild proposal predict for the same XYZ stimulus and viewing conditions. The calculation runs in your browser.
Results
Appearance correlates
Reference result for the example inputs.
| Correlate | CAM16 | 2022 proposal |
|---|---|---|
Lightness J | 59.1305 | 59.1305 |
Brightness Q | 232.561 | 79.1392 |
Chroma C | 49.8664 | 34.4892 |
Colorfulness M | 51.8353 | 45.5003 |
Saturation s | 47.2111 | 57.494 |
Hue angle h | 45.64 | 45.64 |
Shaded rows are redefined by the proposal. The columns use different scales, so their raw magnitudes are not a color difference and are not directly rankable.
Hue is shown only when the opponent response is large enough to distinguish a direction from floating-point cancellation.
Model implementation 1.2.1
What the models report
Both models describe appearance with lightness J, brightness Q, chroma C, colorfulness M, saturation s, and hue angle h. The proposal preserves J and h while changing the definitions and scales of the other four correlates.
These outputs are not display RGB, a color-difference score, a measurement, or a verdict about which model predicts observers better.
Why viewing conditions matter
The same XYZ can appear different as the adopted white, background, surround, or adapting luminance changes. A plausible-looking result under the wrong condition is still the wrong calculation, so every condition stays visible and editable.
Why compare the formulations
The 2022 proposal revisits linked brightness, chroma, colorfulness, and saturation relations in CAM16. Its published fits improve for brightness and chroma but decline for colorfulness—a mixed result, not a universal replacement. See the equation study or use the Python and JavaScript source.
The public suite runs on Windows, macOS, and Linux and compares both models against an independent implementation over 1,512 declared conditions.