http://techon.nikkeibp.co.jp/english/NEWS_EN/20080407/150114/

"A research group at Ehime University developed a pulse drive control method
to make LEDs look twice as bright by leveraging the properties of how people
perceive brightness."

The magic numbers here seem to be run the LED at 60Hz, with a duty cycle of
5% and it'll appear twice as bright to humans. Works better on Blue & Green
than it does on Red.

At that low duty cycle I suppose it would be safe to overdrive the LED
somewhat too.

Andy.

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