Correct me if I'm wrong....
For a given aperture, lets say a perfectly square subject on an f4 scope covered a 5x5 grid of 25 pixels.
At f8 the same object would be twice the size and have 4 times the area, covering 100 pixels, with the same amount of photons coming in(due to same aperture), four-fold increase in exposure length... but 4 times the detail(pixels).
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