Photometric calculations and tables
A listing of photometric data about many different lights can be found on the Set Lighting Technician's Handbook Web site. These tables list lots of information that may be needed such as lamp designation, weight, and scrim size, as well as beam angle and candle power. Beam angle data allows you to calculate the beam diameter of a light at any distance you choose. Knowing the candle power allows you to calculate foot-candle intensity at any distance.
Some manufacturers provide photometric calculators on their Web sites. ARRI Lighting's Web site features a very nice calculator program.
Use Table A.1 to figure out about how many foot-candles you need to achieve ...