How do high speed spy planes avoid motion blur in their photographs?
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The subjet is far away and the exposure time is not that long.
Compare you looking you the window of a car on a highway, The ground beside you is blurry but a mountain far away barely moves.
The closer the plane is to the subject the shorter the shutter time needs to be. You need film/a sensor with high sensitivity and/or a large lense that let in a lot of light.
As long as the spy plane is flying straight, the subject is far enough away, and there is useable light, blur from the plane’s speed doesn’t become a factor.
If you have a window seat in a flying plane, looking out of your window isn’t really blurry despite being 10s of thousands of feet in the air and going 500+ miles an hour.
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.
Two things:
parallax: things far away appear to move slower. Imagine you are driving 60mph down the road. If you look out the side window the trees will be moving by very fast but the hill off in the background is not moving fast. Since a spy plane is taking photos from a high altitude everything it sees is moving slowly
shutter speed: cameras can set the shutter speed fast enough to eliminate motion blur
Aside from what other folks have been saying, the most important thing here is to prevent vibrations in the Aircraft from shaking the camera.
This means either using specialized lenses, or shock mounting the cameras to eliminate vibration resulting in the best picture a camera is capable of taking.
Spy planes such as the SR-71 Blackbird are capable of extremely high speeds, but they avoid motion blur in their photographs by using high-tech camera stabilization systems and wide-angle lenses that allow for a wide depth of field. Additionally, the planes often fly at high altitudes where the air is less turbulent, which helps to reduce motion blur caused by vibrations or wind gusts. The camera systems used on these planes are also designed to take multiple shots rapidly in order to increase the likelihood of capturing a clear image. Finally, post-processing techniques can also be used to enhance and sharpen blurry images.
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