ios 相机启动动画自定义

如何自定义相机开启时候的动画效果？？苹果默认的好像就是这样的：

xingyinzhu

CATransition *shutterAnimation = [CATransition animation];
shutterAnimation.delegate = self;
shutterAnimation.duration = 1.0f;
shutterAnimation.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseInEaseOut];
shutterAnimation.type = @"cameraIris";
shutterAnimation.subtype = @"cameraIris";
[self.view.layer addAnimation:shutterAnimation forKey:@"cameraIris"];

木呆子