Tuning lighting devices could save billions

Posted by Emma Woollacott

Vision researchers - rather than lighting engineers - say they've made a discovery that could save the US billions of dollars in electricity costs per year.

The Barrow Neurological Institute team says it's possible to tune lighting devices to work more efficiently with the human brain, meaning they can be made to give the same apparent brightness with less power.

It's all about the way humans perceive temporal modulations of light. For example, most light-emitting devices, such as light bulbs, video monitors and televisions, flicker. Faster flicker rates mean the flicker's less noticeable, which is more comfortable to viewers.

But in studying this phenomenon in the brain, the researchers discovered that there is a range of flicker dynamics of light that optimizes the perceived brightness of the light without increasing power.

"We found a temporal sweet spot in visual perception that can be exploited to obtain significant savings by redesigning light emitting devices to flicker with optimal dynamics to activate visual system neurons in the human brain," says Dr Stephen Macknik.

The researchers were testing two contradictory theories of how bright a light appears. Bloch's Law states that the longer a visual stimulus lasts, the greater its perceived contrast  - until the brightness hits a plateau at around 100 milliseconds. For example, a five-millisecond flash will appear half as bright as a 10-millisecond one, but a 200-millisecond flash will be just as bright as one of 400 milliseconds.

The Broca-Sulzer Effect, on the other hand, states that perceived contrast increases with duration initially, but then peaks and falls again.

And the team discovered that the discrepancy between the two wass caused by an intrinsic bias among experiment subjects - which, when corrected for demonstrated that temporal vision actually follows the Broca-Sulzer Effect.

"Researchers have been studying temporal vision for more than 125 years, but because ours is the first experiment of its kind to control for all known forms of criteria, it is the first to accurately measure the role of temporal dynamics in brightness perception," says Macknik.

"Thus, the power savings are ripe for the picking because we can adjust our lighting to flicker to take advantage of this peak in perception."

The researchers estimate that if every light-emitting device in the US - from light bulbs to cellphones - worked at optimal efficiency for the human visual system, it could result in billions of dollars of savings in electricity and power.