Hello. I've made a lab experiment of interference and with a CCD camera photographed fringe pattern which one can understand as a periodic signal. My question is: When I apply an FFT to the image is there any limit to the amplitude information I may get from lower frequencies? I read in the internet that for a 1 sec signal, one may be able to obtain information about only freqs above 1 Hz. Why do I ask this? Because the width of the fringes is of about 1/10 the size of the total image, and I am interested in low frequencies. Now I am processing the image in ImageJ in order to get some information. Thanks in advance.