Dim as Possible

Testing Cree XR-E LEDs... on the right is a single XR-E with L2 Optic mounted. This is driven from the Luxdrive 3021 BuckPuck with about the lowest current that it can supply and still have the LED light - about 5mA! On the left is a 'standard' green LED for comparison.

This is pretty amazing given the Cree can be driven up to 700mA or with 140 times more current.

See Rob's Homemade LEDs for more about this.