我什么时候应该使用UIImagePickerControllerSourceTypePhotoLibrary而不是UIImagePickerControllerSourceTypeSavedPhotosAlbum？

I have an application that allows the user to pick a photo from their device. To do this, I'm using the UIImagePickerController, but the problem is that I'm unsure whether I should be using a source type of I have an application that allows the user to p