Each type of lamp  has a defined ability to provide PAR light at different distances off a plant canopy, the beam angle combined with the spectrum efficiency of the lamp determine how much area is effectively covered at a specific value.

PPFD measures the amount of PAR light (photons) that arrive at the plants surface each second. The PPFD is measured at various distances with a Full Spectrum Quantum Sensor, also known as a PAR Meter. Natural sunlight has a PAR value of 900 - 1500 uMol/m2,s when the sun is directly overhead. Essentially PPFD and PPF are the same measurement when taken at the surface of the canopy. Lamps are measured with the PPF standard. 

The below charts may be helpful so you can determine just how far off your plants you wish to place each type and power of lamp to achieve the results you seek.

More graphs are forthcoming.

The 8 bar 840 Watt V-Series lamp produces as much or more PPF as the sun does at high noon at 12" off the canopy over a 4' X 4' area. With overlapping beams from adjacent lamps this is enhanced further.