Mod to decrease brightness/increase runtime?

[carl]

I plan on purchasing the new Underwater Kinetics 3AA eLED. It starts at 60 lumens and averages 40 lumens which is more than I need. How can I mod the circuit to decrease the brightness to 10-20 lumens? Thanks for your help.

http://cotradeco.com/products/1781-3aa-eled-cpo-front-switch-c1-d1