A luminous efficacy model for a white light-emitting diode (LED) cluster was developed, and five alpha-opic efficacy ratios (gamma(alpha,V)s) of intrinsically photosensitive retinal ganglion cells were adopted in order to quantify its nonvisual performance relative to natural light. A tunable C/A/R LED cluster, which consists of the cyan LEDs with green phosphor excited by a blue LED, the amber LEDs with green and orange phosphors excited by same blue chip, and the red LEDs, was proposed by maximizing the average luminous efficacy at correlated color temperatures (CCTs) of 2700 to 6500 K under the condition of color fidelity index (R-f) above 96 and five values of gamma(alpha,V)of 0.95 to 1.05. The real tunable C/A/R LED cluster with aR(f)of 95 to 96, five values of gamma(alpha,V)of 0.97 to 1.01, and a luminous efficacy of 114 to 120 lm/W at a CCT of 2670 to 6456 K were demonstrated. Furthermore, five values of gamma(alpha,V)can be adjusted according to the distance from the Planckian or daylight locus on the CIE 1960 uv chromaticity diagram at different CCTs. Thus, the tunability of gamma(alpha,V)value of the C/A/R LED cluster at a specific CCT could be applied to different requirements for nonvisual performance.