NavList:

"My intention was to take the time the LL of the Sun kissed the top of the opposite hedge to minimise refraction and get me home sooner for the usual ‘gentleman of a certain age’ reason. This was not a good idea. Even so close to the horizon, the Sun soon brings on (hopefully only temporary) blindness"

This should perhaps be counted as a clue. The brightness of the Sun is reduced by extinction when it is near the horizon. Extinction, like refraction more famously in celestial navigation, depends dramatically on the true altitude in the sky. When you look at the Sun setting behind a hill, it's "like" a sunset, but in terms of the visual appearance of the Sun it's different. The Sun remains brilliant and impossible to glance at. It also retains that near-white color it has when it's high in the sky.

A difference of only 15 minutes of arc in altitude can take the Sun from painfully bright to (almost) comfortable viewing. That difference is a crude measure of the actual altitude of the Sun. Also, as the Sun gets close to the horizon, scattering, which is related to extinction, scatters the blue light out and makes the Sun appear progressively orange and then even red. The decrease in brightness, the deep orange color, and the flattening of the Sun's disk are all conquences of the Sun's very low actual altitude. If instead the Sun is setting behind a gradual hill that is imperceptibly different from a level field, seemingly setting as normal but actually a degree or even two or three degrees higher in the sky than you might hope, it will appear brighter, whiter, rounder.

Frank Reed