Basic parameters are taken from Maya.
Number of blades of the Shutter (Affect on Bokeh effect)
0 - Circle
3 - Triangle
4 - Square
5 - Pentagonal...
Sharpness of blades -
0 is flat, 1 is circle
Rotation of the blade
Size coefficient, if you not use real scale for the scene.
Increase or decrease the size of focused area (It will create Macro effect)