How to use SIFT/SURF as features for a machine learning algorithm?

Question

Im working on an automatic image annotation problem in which im trying to associate tags with images. For that im trying for SIFT features for learning. But the problem is a

Answer 1

You should read the original paper about SIFT, it tells you what is SIFT and how to use it, you should carefully read the chapter 7 and rest for understanding how to use it practically. Here is the link for original paper.