How do high speed spy planes avoid motion blur in their photographs?
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Contrary to what most people say here, you can’t rely on distance & short exposure only: “spy” aerial photography needs high resolution, lighting isn’t always perfect, so movement blur will happen/be noticeable if not taken care of.
In olden times the camera onboard was equipped with a mechanism which moved the film during exposure, forward in the plane’s flight direction as the lens inverts the image, that movement being set according to the plane’s height and speed and the lens’ focal length (longer, telephoto lens, and the image of the ground moves faster).
Thus the image remained stationary on the film and you got a sharp picture.
I don’t know how exactly it’s done nowadays, but I’m quite sure that an equivalent electronic process is at work: individual ultra-short (necessarily dim) shots get shifted and combined in software to make a full-bodied image, similarly to what happens when a video is stabilized.
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