Have you ever turned a light off just to realize there's another light that is now way too bright but wasn't bright enough when the lights were on? Like an annoyingly bright nightlight.
I have an LED light string that I'm going to use to accent the back of a canvas painting. I wanted it to have a brightness equivalent to the ambient light shining on the painting. The lights can either be powered by a USB battery pack or any USB outlet that can supply 220mA of power at 5v.
(Max power consumption is just over 1 watt and drops below 1mA in darkness. A small 2200mAh battery pack should last 7-20 hours depending on lighting conditions)