The fluorite lenses also allow them to shrink the lens design and make it easier to carry around. They do this by reducing the # of elements required. It's w

The fluorite lenses also allow them to shrink the lens design and make it easier to carry around. They do this by reducing the # of elements required. It's why you mostly see them in big long focal length lenses since that's where the size & weight gets really obnoxious.