Field emission from individual tips in a silicon field emitter array (FEA) has been directly evaluated by using an electrostatic lens projector. Uniformity of the emission sites in n- and p-type Si FEAs has been investigated and compared at various conditions. The number of the emission spots in the p-type FEA increased linearly with the increase in the total emission current, and the p-type FEA exhibited better uniformity of the emission spots especially under large emission currents than the n-type FEA. Furthermore, effects of the gas ambient on the emission uniformity were evaluated. The emission uniformity was improved dramatically by exposing C2H4 ambient during the field emission.