The F2^n numbers make sense as standards. What is the justification or origination of the other set of F22-F1.4 values.

Helen-Yang

These values are a geometric series of powers of the square root of 2 (rounded to 1.4). The square root is from halving the area, which corresponds to the radius/diameter being reduced by a factor of sqrt(2). https://en.wikipedia.org/wiki/F-number

The F2^n numbers make sense as standards. What is the justification or origination of the other set of F22-F1.4 values.

These values are a geometric series of powers of the square root of 2 (rounded to 1.4). The square root is from halving the area, which corresponds to the radius/diameter being reduced by a factor of sqrt(2). https://en.wikipedia.org/wiki/F-number