This tool uses a polynomial approximation of the Planckian locus and returns an approximate Duv value suitable for quick analysis.
What is Duv?
Duv is a color quality metric that describes how far a light source sits from the blackbody (Planckian) locus on the CIE 1960 u,v chromaticity diagram. In plain English, it tells you whether a white light appears slightly greenish or slightly rosy at a given color temperature.
- Positive Duv: usually appears greener/yellow-green relative to the blackbody reference.
- Negative Duv: usually appears pinker/magenta relative to the blackbody reference.
- Duv near zero: very close to the blackbody curve (often perceived as more neutral).
How this Duv calculator works
The calculator accepts either CIE 1931 x,y coordinates or CIE 1960 u,v coordinates, plus your CCT (correlated color temperature). If x,y are provided, they are converted to u,v first. Then the tool:
- Estimates the Planckian locus position at your selected CCT.
- Builds a local normal vector to the locus.
- Projects your test point onto that normal to determine the signed Duv.
Input guidance
1) Using x,y data
Use this mode when your meter or software reports CIE 1931 chromaticity coordinates. The calculator internally converts:
u = (4x) / (-2x + 12y + 3)
v = (6y) / (-2x + 12y + 3)
2) Using u,v data
Use this when your instrument already reports CIE 1960 coordinates. This avoids an extra conversion step and keeps the workflow straightforward.
How to interpret your result
There is no single “perfect” Duv target for every application, but practical ranges are common:
- |Duv| ≤ 0.0015: Very close to blackbody (typically neutral for many uses).
- 0.0015 to 0.004: Slight tint shift; may be acceptable depending on context.
- > 0.004: Noticeable cast (green if positive, rosy if negative).
Where Duv is especially useful
LED selection and binning
Two fixtures with the same CCT can still look different on camera or to the eye. Duv helps explain those differences and improves fixture matching.
Photography and filmmaking
Mixed lighting can create subtle color contamination. Monitoring Duv can reduce correction effort in post and improve skin tone consistency.
Architectural and commercial lighting
In retail, hospitality, and office spaces, small tint shifts can influence product appearance and visual comfort. Duv can be a valuable quality-control signal.
Limitations and best practices
- This calculator uses an approximation model for Planckian locus coordinates.
- For laboratory-grade reporting, use calibrated spectroradiometric software and full uncertainty analysis.
- Always evaluate Duv alongside CRI, TM-30, illuminance, and spectral power distribution (SPD).
- Perception varies by adaptation, surroundings, and observer sensitivity.
Quick FAQ
Can two lights have the same CCT but look different?
Yes. Duv explains much of that difference by indicating whether each source sits above or below the blackbody locus.
Is negative Duv always better?
Not always. Preferences depend on application, culture, context, and brand standards. “Better” is use-case dependent.
What CCT range does this tool support?
This page supports inputs from 1000 K to 15000 K for stable approximation behavior.