by CHI-TOWN » Thu Feb 23, 2012 5:37 pm
There are literally thousands of different leds and different drive currents so the number of LEDs is not as important as the LED type, model, color temp, drive current, power, ...etc
I would use the lights lumen output @ 12vdc source voltage.
These rock lights are mounted at what about 12 to 24 inches above grade ?
For instance if you use a cool white LED then you can use less power and actually render the objects in view better. Your eyes will percieve the objects better and be able to differentiate between solids and shadows better than with a warm white light.
I have some 3 led pods that kick out 20 lumen per light and run on 12vdc. They illuminate a small area (10' x 10') very well. Now I am thinking with 8 of them on a truck underbody it should be more than enough light to illuminate the terrain surface to about 2-4 footcandles