Studying potential colour shifts in White LED’s while dimming in order to understand the measured aspects of correlated colour temperature (CCT) and other colour metrics.

My interest towards this topic started when I was interning. Manufacturing representatives would come in to show us their new products but would seldom speak about dimming and what happens to all of the properties when dimmed. Nor did I ask. So, this thesis is a result of an exploration of my curiosity and questions of what happens when LED's are dimmed. In specific what happens to the colour temperature and colour metrics.

With the invention of LEDs and rapid growth in technology, there is still this vigorous drive to mimic the “good old” incandescent. While incandescent lamps change correlated colour temperature (CCT) while dimming, the general assumption and conventional wisdom is that LEDs do not change in CCT when dimmed unless they are warm-dim technology. Is this an assumption or reality? The lighting industry relies on metrics to report, evaluate and predict how a fixture is going to perform. Information regarding CCT and other properties like SPD, CRI and CIE chromaticity coordinate values of LEDs, when they are dimmed is not readily available. This paper will focus on evaluating white LED’s when dimmed by evaluating the measured changes in advanced metrics like the TM-30, CIE chromaticity and CRI for different sources. This data will be crucial in the lighting industry to manufacturers and designers as they develop and specify fixtures particularly in applications where colour is very critical and where sources are almost always dimmed, like museums and restaurants.