The ability to dim LED fixtures smoothly without affecting the colour is crucial to their acceptance. Internal dimming software controls this part of the fixture’s performance. “It takes a lot of time to calculate all of the dimming combinations across all of the different colour combinations and is a heavy development investment. The companies that care about the quality of light pay attention to details like this, and it’s an easy way for a user to see the difference between good and bad design,” points out Mark Ravenhill of GLP (pictured).
However other factors come into play, he says: “One of the difficulties is that the intensity of a light will affect one’s perception of colour of a fixture. The colour may not actually change, yet we may see it happen. However, we’ve done everything we can to prevent actual drifting of colour throughout the dimming curve. We’ve also included a feature called Red Shift that mimics the warming up of colour temperature of an incandescent lamp. Designers think it looks natural and familiar. They know what they want their colours to look like at full or at 50%, and we want to enable that way of working.”
According to Adrian Searle, head of technical and hire at Stage Electrics, dimming of profile lanterns had undesirable effects, although these are now being overcome. Early products, he observes, “did not follow the low-end dimming curves correctly and would cut off, so were not suited to the romantic slow fade to black.” The introduction of 16-bit dimming control, in place of 8-bit, gave the necessary reduction in dimming step to achieve this and a rise in refresh rate to 2.8Khz from the original 300Hz has further improved the visual effect by removing flicker and creating camera-friendly lighting for TV broadcast.