WELL-ROUNDED APERTURES

More diaphragm blades usually equates to better rounded apertures, but it’s not always the case

Alarger number of diaphragm blades enables the aperture to retain its circular shape better when you stop down from the widest setting. The roundness of the aperture depends on how much the diaphragm blades are curved. Most lenses in this test have well-rounded apertures based on nine diaphragm blades. The Canon 50mm f/1.4 and 85mm f/1.8 have eight-blade diaphragms and the Canon 50mm f/1.8 only has a seven-blade diaphragm. Still, the aperture of the 50mm f/1.8 looks better rounded and many prefer the effect produced by an odd, not even, number of blades.

Stopping down, defocused lights take on a rounder appearance with the Canon f/1.8 lens, compared with the f/1.4, despite it having seven blades