How to use SIFT algorithm to compute how similar two images are?

Question

I have used the SIFT implementation of Andrea Vedaldi, to calculate the sift descriptors of two similar images (the second image is actually a zoomed in picture of the same

Answer 1

You should read David Lowe's paper, which talks about how to do exactly that. It should be sufficient, if you want to compare images of the exact same object. If you want to match images of different objects of the same category (e.g. cars or airplanes) you may want to look at the Pyramid Match Kernel by Grauman and Darrell.