We present a new model for multiple input multiple-output (MIMO) out door wireless fading channels which is more general and realistic than the usual i.i.d. model. We investigate the channel capacity as a function of parameters such as the local scattering radius at the transmitter and the receiver, the distance between the transmit (TX) and receive (RX) arrays, and the antenna beamwidth sand spacing. We point out the existence of pinhole channels which exhibit low fading correlation between antennas but still have poor rank properties and hence low capacity. Finally we show that even at long ranges high channel rank can easily be obtained under mild scattering conditions.