I feel like flat earthers don't understand perspective and refraction.
Perspective works using light as travelling in straight lines from a light source or from an object which the light has bounced off. It is very simple to understand, simulate, calculate and does explain almost all our observations on a spherical earth, apart from when refraction is involved and light bends over long distances mostly just over the surface of earth, and very slightly when viewing up through the atmosphere.
Refraction bends light as it travels through mediums of different density, which is easily demonstrated.
The atmosphere can cause refraction when there is a high gradient density difference, this shows easily in videos and pictures as moving blur, and will result in either light bending upwards (when the density is lower close to the surface), and bending downwards (when the density is higher close to the surface).
The amount of bending is minuscule, and it is only noticeable over long distances, primarily over water watching from a beach or harbor.
The result of light bending upwards, will result in a vertically compressed visual of the objects near to the horizon, or in more extreme cases a vertical flip (mirroring effect) which can be compressed, normal or even stretched in even more extreme cases. The viewing distance to the horizon is also shortened due to light bending upwards.
Normally hot weather will result in this behavior above water.
The result of light bending downwards, which happens less frequently, will result in a vertically stretched visual of the horizon, and will result in a further viewing distance than normal as light will bend with the spherical earth.