The purpose of this investigation is to quantify the influence of the peak wavelength shifts in commercially available LEDs on the characteristics of the mixed-LED white-light sources. For this purpose, a tetrachromatic spectrum was optimized and then subjected to deviations in the peak wavelengths. A total of 882 combinations of peak wavelength values were evaluated, and the results are reported in terms of correlated colour temperature, colour-rendering properties, and radiant luminous efficacy. The results show that there can be significant changes in the characteristics of the source under these conditions. Such changes are highly likely to present problems when dealing with applications where an effective and accurate white-light source is important. 1. Introduction White light can be produced by additively combining the outputs of multiple monochromatic light-emitting diodes (LEDs) [1–6]. Thus, by fine-tuning the spectral intensity of individual LEDs, which emit different narrow bands of radiation, a white-light source characterized by a good colour-rendering index, , and high luminous efficacy of radiation, , can be designed. Creating a stable white light using multiple LEDs is a complex task since both colour rendering and luminous efficacy of the mixture depend on the emitted spectrum of the individual LEDs. Therefore, any change in the LED parameters (peak wavelengths, spectral widths, lumen outputs, etc.), for example, due to variations in junction temperature of the LEDs, causes a change in the spectrum of the LED devices and consequently a change in the spectrum of the white-light source [7, 8]. The amount of change will depend on the magnitude of the deviations for each LED in the mixture. Keeping the mixture stable is further complicated by the fact that different types of LEDs are affected differently even when they are working under the same conditions [9]. Therefore, designing a simple yet accurate control system to maintain the white point within acceptable tolerances is one of the key challenges [7, 8, 10, 11]. We demonstrated that white-light sources based on LEDs have the potential of becoming the optimum choice for high-colour-rendering tasks [1], and in [2] we introduced our approach to intelligent spectral design. However, implementing a stable mixed-LED white-light source based on a theoretical (optimized) spectrum is an exacting task since there is no guarantee that a given set of real LEDs will exactly match the parameters used during the spectrum design. Hence, we have investigated the sensitivity of an optimized 4-band LED
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