Quote:
Originally Posted by Sully2
No idea what math formula you are following?? But its sure not "area=pi r squared"???

It's true that
is the formula for finding the area of a circle, but when comparing the areas of 2 different circles the constants and common factors in the expression will cancel. So you can use diameter, radius, or 57.35 times the radius of each circle and you will arrive at the same ratio when finished...which in this case is a ratio of 1.2544:1. So there is 25.44% more area on a 56mm lens when compared to a 50mm.
It's really a trade off though. Bigger, heavier, and usually more expensive is the price you pay for having a brighter image at dusk and dawn.