For a 1-D fft, the process is as follows:
fs = %arbitrary sample frequency
N = length(signal);
fbins = [(0:1/N:1-1/N)*fs]; %frequency bin vector for plotting (x axis)
calval = N/2; %for two-sided ffts, calval should just be N for one-sided
[fftdat] = fft(signal);
fftmag = abs(fftdat)/calval;
%to visualize that expected magnitude is correct
figure
hold on
plot(fbins, fftmag)
See if you have any luck with a similar approach for your 2-D fft.
