About frequency analysis of luminance image (csv). 2D Fourier (fft2).

About frequency analysis of luminance image (csv). I am dealing with images (luminance image 3840×3841, angle of view is 29 degrees), and I would like to analyze the frequency (cycle / degree). What I want to know is how much frequency band (cycle / degree) is included (in frequency spectrum etc.). I don't understand the procedure after doing 2D Fourier (fft2). If you know anything, please let me know.