The code used to generate these images is available here.
 
The spheres are the same size. There is no motion in the scene.
 
Aperature: 0 (pinhole)     d: 5.0
 
Aperature: 0.5     d: 2.5
 
Aperature: 0.25     d: 2.5
 
Aperature: 0.5     d: 5.0
 
Aperature: 0.25     d: 5.0
 
Aperature: 0.5     d: 7.5
 
Aperature: 0.25     d: 7.5