When I apply corr2 to two similar images (delay between two consecutive images of 1s) it gives correlation coef. close to 0.99 but when I use corr2 for two similar flat field normalized images (delay around 1s between the images) correlation coef. is close to 0. Why is that? Do I have any options other than the built-in corr2 to determine the degree of correlation between two images? I would like to try several approaches to track the correlation between two images (linear and non-linear correlation).
You're probably making a mistake with the normalization.
Here's an example that doesn't change the correlation coefficient:
im1 = imread('cameraman.tif'); im2 = imnoise(im1,'gaussian'); corr2(im1,im2) %0.9286 im1n = double(im1)./sum(sum(double(im1))); im2n = double(im2)./sum(sum(double(im2))); corr2(im1n,im2n) %0.9286