Find large distinctions in Video Assume you have 77777 pictures that are mostly noise. 
They are about magnetic anisotropy. 

There is one picture among these pictures which has high contrast difference between two large areas (some sort of magnetic gap because of magnetic anisotropy). 
One area is gray and the other area is dark. 

The pictures are mostly like this (grey or dark)



and



There are some dirty things in some pictures which are just rubbish on the lens. 
So only big differences are essential. 
Example what the contrast difference should look like 



These pictures are about magnetic anisotrophy with Fe and Boron.

How can you find the distinction among these 77777 pictures?
I have went through all of these pictures but my method is errorprone, since I just browse them through. 

How can you assist browsing the find the big and large contrast difference in pictures?

Any tool is ok for me: Matlab, Python, ..., pseudo-code too.
Implement a low pass 2D filter that will reduce greatly the noise. 
Following an example that you could complete yourself. 
You could subtract the filter bias to keep an average of 0 "addition" by the filter, controlling the dynamic range.

Example of filter

         1/16  1/8   1/4  1/8   1/16

    1/16  1/8   1/4   1/2  1/4   1/8     1/16

1/16  1/8   1/4   1/2   1    1/2   1/4     1/8     1/16

1/8   1/4   1/2   1     2    1     1/2     1/4     1/8

1/16  1/8   1/4   1/2   1    1/2   1/4     1/8     1/16

   1/16  1/8   1/4   1/2  1/4   1/8     1/16

        1/16  1/8   1/4  1/8   1/16


You might be able to clearly see the desired image.

Than run an Edge a 2D edge detector which will enhance the location of the step.
You could try running two 1D filters: -1 1 in horizontal and vertical direction. If you know the relative "black"/"white" areas you could select which to use of the optional -1 1 or 1 -1.

You might be able to use frequency domain filtering for the low pass 2D filter. 
If you are not familiar with this type of challenges and this is not exercise you need to get a consultant to help you or study the subject in more depth.

Depending of the contrast of the "step" you might be able to detect automatically the "line" created by the edge detector.