CABasicAnimation shrink effect the animation look very jerky

Question

Any suggestion how can i improve it the size of image intially is 2000*1500

CABasicAnimation* shrink = [CABasicAnimation animationWithKeyPath:@"transform.scale"];
shrink.toValue = [NSNumber numberWithDouble:0];
shrink.duration = 15.0f;
shrink.fillMode=kCAFillModeForwards;
shrink.removedOnCompletion=NO;

shrink.delegate = self;
[imageview.layer addAnimation:shrink forKey:@"shrink"];

reference from http://stackoverflow.com/questions/617992/how-do-i-chain-scale-animations-with-an-iphone-uiimageview