loglog plot and fft2

[Paolo Zaffino]

Hi at all!
I must compute the power spectrum density of an image.
For this reason I run:
psd=sqrt(abs(fft2(img)));
and it seems ok.
Now I'd like plot into a loglog graph the spectrum of the 2D Fouriere 
trasform (frequency vs magnitude)...Could anyone help me?
Thanks a lot!