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If both the subject and the camera are located on Earth (or any planet), the distance to the horizon is an upper bound. As explained in the link, with the camera at 1.7 meters above the ground and assuming a spherical planet, the curvature of the Earth limits sight to about 2.9 miles not counting any refraction caused by temperature changes in the air ...


This is not a practical answer (it is not a practical question), but it is a precise answer. Let's define "not visible". If in an image, I will offer a description of "not visible" that the object is not more than one pixel size in the image, which certainly will not be considered visible (probably 5 or 10 pixels works as well ...), but "it depends", on ...


I will just give you a glimpse of what are you asking, so you can do your own math. We need to take in account: The object 1) What is the color. Diferent colours have diferent wavelengths, so this affects on the sensor reception, difraction, atmospheric absortion, etc. 2) The contrast with the background. This is pretty obvious, a white board on a white ...


Under bright sunlight conditions, a young person with 20/20 vision can resolve an object that is approximately 3000 diameters distant. A 2 meter square object has a diagonal measure of 2.8 meters. This object if viewed from 2.8 X 3000 = 8,400 meters, will appear to be a point without discernable dimension. The 3000 times its diameter rule of thumb is too ...


There is no "one answer", it depends from too many variables. It depends on the size of the object, the focal lengh of the lens mounted on the camera, the resolving capability of the lens (its optical resolution, so to say), the resolution of the sensor...and the definition of "not visible" for who is watching the final image. Uh, and the type of light ...

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