Optical and X-ray spray measurements may yield different results when similar quantities are measured. Computer simulations were used to reconcile such differences in the near-nozzle region for high-velocity, dense fuel sprays injected into nitrogen at various gas pressures. It was found that the near-nozzle region consists of a dense core around the spray axis, which contains the majority of the liquid mass, and its radial expansion is not very sensitive with respect to changes in the gas pressure. The remaining liquid mass forms a dilute region away from the spray center; it is responsible for the formation of the optical spray angle and hence varies with the gas pressure according to the known experimental correlations. Further, injection pressure variations of sprays into SF6 gas showed that the radial expansion of the dense core and the dilute periphery are independent of the injection pressure.