Computing and plotting the PSD multiple images by fft2

Hello,

I have a a folder which contains around 2500 frames were divided from a vido of a wter tank experiment. I am trying to plot the "average" 1D & 2D PSD for the whole images(i.e. (psd1+...psd50)/50;

I have tried many aproaches, but I am not sure about the output.

Here is my code:

min=zeros;
min_1D=zeros;
   for K = 1 :1500:75000
      this_file = strcat('folder\frame',num2str(K),'.tif');
      im_input = imread(this_file);
      im_input = rgb2gray(im_input);
      
       %%%%
      SLength=length(im_input);
      Fs=500;
      dt = 1/Fs; 
      q=round(SLength/2);
      f=(1/dt)*(0:q)/SLength;
      TX_1=fft(im_input);
      Px1=abs(TX_1/SLength);
      Pxx1=Px1(1:q+1);
      min_1D=min_1D+Pxx1;
      %%%%%
      
      zfmin=fft2(im_input);
      shiftmin=fftshift(zfmin);
      min_2D=abs(shiftmin);
      z_min=log10(min_2D);
      min=min+z_min;
   end
   PSD_2D= (min)/ 50;
   PSD_1D = (min_1D)/ 50;
 figure,
imagesc(PSD_2D)
colormap gray

• Do I have to substract the mean>

 TX_1=fft(im_input-mean ((im_input))?

btw the actual length is 0.2398 mm/pixel.

I appreciate your feedback and comments.

Thanks