Need help in 2D fast fourier transform

I have a 2D array, one dimension for x and one dimension for t(with interval dx and dt), the data in the array indictaed the amplitude at that x and t. I used the fft2 to do the fourier transform as shown below:

Y = fft2(array);
Yshift = fftshift(Y);

f1 = figure;
imagesc(abs(log(Yshift)));
colorbar;

and get the figure as this:

how can I change the scale value on the axis into the value of the true frequency and wavevector? Since now it is just number of the points.

And BTW, is there any way that I can always get the best contrast?

Thanks a lot.