A light rail in most situations is designed to simulate the movement of the sun throughout the day in the sky. Great if you want to get more planting area covered with less lights.
hope this helps.
LS

any estimates in percent of the increased planting area?

With my 400 hps 2 1/2 times as much. Hope it helps.You'll have to adjust it so you don't get lanky plants on the ends or the middle ok. Good luck.

how much closer do you move the light to the plants?, or is this a lot of trial and error?

ya sorry for the misunderstanding on my part what I mean about lanky is that if you have the light mover set to stop on the ends to long then the plants on the ends will get taller then the ones in the middle and to tall in the middle if you have it adjusted to short of a time on the ends.so ya it is alot of trial and error for your 1 st or 2 nd go at it.the key is to have uniform growth.keep a log of temp humidity nut.this will definiltly HELP in future goes.how i did the distance fromlight to plants was have it as low as it could be with out burning them.when I noticed the first sign of burn I put a piece of tie wire from light to the top of canopy and as plants grew( wire starting to graze top of canopy) I raised the light (metal chain from mover to light with s hooks).just remember these lights will cause fires if not hung correctly so use good heavy enough hardware.ok

Does using a light mover decrease the effect? I mean, if a high-light plant is recieving 2000 fc constantly wouldn't that be better than 2000 fc then 500 fc (when the light is 6 feet away) and back all day long?

2000 fc constantly definitely is better than 2000 then 500 then back to 2000.

but with the light mover and a metal halide bulb, the light can be moved closer to the plants with decreasing the chances of leaf burn. you will get spikes of fc's that will higher than 2000. so you may go to 5000 fc when the light is directly over it, but the time period of each spike in intensity may be short enough so that burn doesn't develop. then when it moves away, the fc will drop. so essentially you can make the total foot candle HOURS about the same(ie. the sum of foot candles multiplied by time),but you have a bigger area to grow things.

I hope this makes sense..I am new to this also. It's gonna be trial and error in my basement. I hope I don't kill anything.

who knows, it may even be better for the plants. its like the sun moving through the sky and the spikes in foot candles occur when the sunshine can make it through breaks in the forest's canopy

Or like mimicking a partly cloudy day, perhaps??