tweak intensity of blur effect inside UIVisualEffectView in Swift

The radius of the actual UIBlurEffect cannot change, but there is a workaround.

Changing the alpha component of the UIVisualEffectView, will give a subtle blur effect.

let blur = UIVisualEffectView(effect: UIBlurEffect(style: UIBlurEffectStyle.Light))
blur.frame = CGRectMake(180, 10, 200, 750)
blur.alpha = 0.4
myView.addSubview(blur)

Swift 3

let blurEffect = UIBlurEffect(style: UIBlurEffectStyle.extraLight)
let blurEffectView = UIVisualEffectView(effect: blurEffect)
blurEffectView.alpha = 0.4
blurEffectView.frame = self.bounds
self.addSubview(blurEffectView)