The ratio can be determined in relation to F stops since each increase in f-stop is equal to double the amount of light: 2 to the power of the difference in f stops is equal to the first factor in the ratio.
The ratio can be determined based on the relationship between f-stops and light intensity, where each increase in f-stop doubles the amount of light captured. The ratio is calculated by raising 2 to the power of the difference in f-stops.