Flat Earth Lies: A fisheye lens can not invert a curve, only emphasise it

I see variations of this claim a lot "A fisheye lens can not invert a curve, only emphasise it" which Flat Earthers use to insulate themselves from the fact that you can, in fact, use images from curvilinear lenses to see the accurate curvature of the Earth.

This is complete and utter nonsense.

Here is a convex curve I created on a grid:

And here is it with fisheye distortion -- I added the straight red line for comparison (without it the green line looks bent due to the visual illusion):

Why do Flat Earthers lie like this?  They MUST know they haven't tested these claims but they present this nonsense as if they have.

Why isn't the text super distorted?  Simple, the distortion near the center of the lens is minimal.

Cara Diann explains in excruciating detail about curvilinear lens distortion:

So, when you see this, with the horizon just passing through dead center of the lens, you are actually seeing LESS curvature than actually exists due to the lens distortion.

GoPro Awards: SL-10 rocket, Mach 5.5, altitude of 396,000ft, at mark 1:51

Another way to eliminate the lens distortion as the cause of the curvature is to simply compares images with the horizon passing through lens center at different altitudes as I've done here in this series from the Rotoflight balloon video -- notice how the horizon curvature increases with altitude (additional analysis):

So, not only can a fisheye lens make the convex curvature of the Earth look "flat", but by carefully looking at how fisheye lenses work we can reliably show the Earth's curvature using them.

Also remember that the Horizon is NOT a curve of 3959 miles radius but rather is a much smaller circle that is curving around the observer formed by the observer line-of-sight tangent to the spheroid of the Earth -- discussed in greater detail in my post on the Horizon curvature.