[ptx] Questions on Lowe's SIFT algorithm

[Xianyong Fang]

Hi All,

	I find that the SIFT algorithm of Lowe's paper is not robust to scale transform. When I try to register two images with different scales, there are few (or not so many correct) matches existing. To images with rotation and different scales, it works even worse.  But when I apply the sift algorithm to images with simple shift or small rotation, it works fine and almost all the returned matches are correct.  Does anyone have the same experience with me?

    I also find that in Lowe's IJCV paper "Distinctive Image Features from Scale Invariant Features" the testing images showed almost have the same scale. I can't help thinking that maybe his algorithm is hard to copy with images of different scales.

    In addition, I also try to intergrate "PCA-SIFT: A More Distinctive Representation for Local Image Descriptors" into the matching process and find the same problem. 

Xianyong