If you do not know the collection's Amazon Resource Name, you can use the DescribeCollection operation.
Adding faces to a collection
NoteDetectFaces returns the same information, so you don't need to call both DetectFaces and IndexFaces for the same image.
To use quality filtering, you need a collection that's associated with version 3, or higher, of the face model. To get the version of the face model associated with a collection, call DescribeCollection.
Searching for a face (image)
If the service detects multiple faces in the input image, it uses the largest face that's detected for searching the face collection.