## Fisheye Lenses and Lens Distortions

A photographic lens may have a specific distortion characteristic and strength that may differ from another lens. However, despite the differences, a straight line will always appear straight if it crosses the center of the frame.

Flat-Earthers like to dismiss images taken by a fisheye lens. In reality, the attributes of such a lens are well known. We can use the knowledge to determine if a line in the image is straight, even if it was taken using a fisheye lens.

## The Lack of Motion Blur in Earth Photos

The surface of the Earth close to the equator is moving at the speed of about 1670 km/h due to Earth’s rotation. To take a sharp picture of the Earth with the resolution of 10000×10000 from a stationary position in space, it would require the shutter speed faster than 2.7 seconds. It is not difficult at all to take a sharp picture of the entire Earth without perceivable motion blur.

Flat-Earthers claim that it should be impossible to take a sharp picture of the Earth from space due to the speed of Earth’s rotation. To them, the fact that a photographer cannot take a sharp photo of a speeding race car from the sidelines (they actually can) tells us it should be impossible to take a sharp picture of the Earth moving at 10× the speed.

They are wrong. Motion blur is caused by the angular speed of the object relative to the camera, not from its absolute speed. The vast distance required to take a photo of the Earth results in a very low angular speed, making it not difficult at all to take sharp images of the Earth.

## Real Photos of the Earth

The first photo showing the entire Earth was taken in 1966 from the spacecraft Lunar Orbiter 1. Since then, there are too many photos showing the whole earth taken from various missions to space.

The advent of computers in the 80s introduced a new technique of generating such pictures. A satellite can be used to take many photos of the Earth from a low orbit, and computers can be used to assemble those pictures into a single photo of the Earth.

Flat-Earthers ‘discovered’ such technique, then they concluded that all pictures of the Earth taken from space are all composites, the results of manipulation or assembled by computers. They are wrong. Just because there were pictures created using such technique, it doesn’t mean there is no genuine picture showing the entire Earth, not composites, not stitched, and were taken from a single shot.