Originally Posted by
Pere Casals
Well, in reconnaissance an important parmeter is the on "ground motion blur", this depends only (if no compensation) on shutter speed and ground speed, and it tells what object size we can see because blur. At Mach 1.0 this is 340m/s, so at 1/1000 shutter we have 340mm ground blur. At Mach 0.5 this would be 150mm of motion blur at real ground object scale, so the AK-47 stacks had to be seen.
Given the flight altitude and the focal we can calculate the "on film blur", this is the "on ground blur" divided by the magnification. If Magnification is 1:5000, then those 150mm of ground blur will be 0.03mm of motion blur on film, so limiting resolution to some 15 Lp/mm, so we can go x3 higher with the plane and still motion blur not degradating what sharp film/optics can capture, or using a 1/3 of the focal length at same altitude....
At the end the ground motion blur will determine the size of the field that the photograph can record without degradating what motion blur allows...
I make that kind of calculations often, but with an industrial camera looking moving products, it's just the same easy calculation. In fact I got the theory from aerial photography handbooks...
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