PRO explanation, I learn something today :thumbsup:lsisaxon said:The area is not increased or decreased linearly. It has to be either doubled or half to increase and decrease by a stop respectively. So if area is doubled or half, the diameter will be multiplied or divided by square root of 2 respectively... which is why the numbers like 1.4, 2.8, 5.6 etc comes in. Square root of 2 is approximately 1.4.