Primary atomization was studied via fast video camera visualizations. The injection device consisted of a planar airblast atomizer, which generated a 300 mu m thickness sheet. The system geometry remained constant, while the fluid's flow was modified to produce a wide range of conditions. In the case of the gas, both the air velocity across the airblast atomizer and its absolute pressure were varied. The latter parameter reached a value of 11 bar. Additionally, water and kerosene Jet A-1 were injected at several velocities. A set of image process algorithms were developed to measure the break-up length, transversal wavelength, and longitudinal ligament sizes from these visualizations. These characteristic behaviors were strongly affected by the atomization mechanism at which they were measured. Four regimes were observed for the range of M from 0.12 to 32. Overall, the magnitude of these characteristics decreased as the airflow pressure augmented. Finally, a set of empirical relations are proposed to predict the magnitude of these characteristics at the tested conditions.