Originally Posted by mopar_guy
I looked at the lenses which I own and counted the blades.
The following Olympus OM Zuiko lenses have six blades: 18mm f3.5, 21mm f2, 35mm f2, 40mm f2, 50mm f1.8, and 50mm f2 Macro.
The following Olympus OM Zuiko lenses have eight blades: 24mm f2, 50mm f1.4, 55mm f1.2, 85mm f2, 135mm f2.8, 180mm f2.8, 300mm f4.5, 400mm f6.3, and 600mm f6.5.
The 100mm f2 ED Zuiko and 250mm EDIF Zuiko both have nine blades.
To add to this, the 200 f/5 has 8 blades, the 100 f/2.8 has 8 blades, and the 50 f/3.5 has 6 blades.