数码相机中，zoom就是缩放意思；也就是镜头变焦的意思，推近或者拉远焦距
/** 调节ZOOM */

• (IBAction)zoomChangeValue:(UISlider *)sender
  {
  NSError *error = nil;
  [self.camereManager.captureDevice lockForConfiguration:&error];
  if (!error) {
  self.camereManager.captureDevice.videoZoomFactor = sender.value;
  }else
  {
  NSLog(@"error = %@", error);
  }
  [self.camereManager.captureDevice unlockForConfiguration];
  }

/** 放大缩小屏幕 */

• (IBAction)viewScaleChnageValue:(UISlider *)sender
  {
  self.previewView.transform = CGAffineTransformMakeScale(sender.value, sender.value);
  }

/**

ZOOM:镜头变焦，推近或者拉远焦距,拍照后有效果
放大缩小屏幕：放大缩小后拍照无效果