I want to know the answer to the following question:
What is the effective f-number proportional to?
All the background I'm provided with is that "The equation may be expressed as ratios, or, by taking the logarithm (base 2) of both sides, by addition, using the APEX system, in which every increment of 1 is a doubling of exposure; this increment is commonly known as a "stop".". Is that enough to answer the question?
Answer: no