Antialiasing

OverSampling. This option turns anti-aliasing on, to achieve 'soft' edges and perfectly displayed Image textures. OSA rendering generally takes 1.5 to 2 times longer than normal rendering.

Blender uses a Delta Accumulation rendering system with jittered sampling. The values of 'Osa' (5, 8, 11, 16) numbers are pre-sets that specify the number of samples; a higher value produces better edges, but slows down the rendering.