I figured out the error in my calculations. I was using radius in places where I should have been using diameter. Thus,1.4, 2.0, 2.8, 4.0, 5.7, 8.0, 11.3, 16.0, and 22.6 are what I get for the exact doubling or halving of light. Now, I am trying to figure out where f-1.8 comes from and how lens makers get away with the cost difference between 1.8 and 1.4. It seems just as easy to make diaphram elements that go open up to either.