That's not what I was talking about. I know the reason for the change of impact at different power settings. I was wondering what actually causes parallex. I know what it is, I just always wondered what made it happen and how the adjustment corrects it.

You read my post wrong, but that's ok. That's why I commented about not wanting to take six years of school to understand the physics behind it. I thought it had something to do with line of sight and focus, but I was just guessing.

Paul