# FFT of 2 D images

Branching off from this question - https://dsp.stackexchange.com/questions/6020/mapping-the-value-of-a-sample-in-a-2-d-dft-to-cycles-pixel, I have a few more questions related to 2D FFT of images.

• I correct in assuming that the fundamental frequency is the image itself?
• And one copy of the image is equivalent to 1 wave cycle?
• The sampling frequency is the number of pixels in the image?
• And If this is correct, how do I compare two distinct images?
• Can I compare the sampling frequencies ( $\frac{1}{N_1}$ & $\frac{1}{N_2}$ ) and frequency peaks of one image with a second image ($\frac{1}{N_2}$)? ($\frac{1}{N_1}$ & $\frac{1}{N_2}$ are the dimensions of an image)

What I am trying to understand is - what the X & Y axis of a complex 2D FFT plot is? and how to compare information from 2 plots?