The Sun appears to be in the angular size of about 0.53°, and it is constant throughout the day. But sunlight is very intense and causes glare that surrounds the Sun. Because of the intensity, we are unable to distinguish the Sun from its glare.
During a sunset, sunlight’s intensity is reduced as sunlight traverses the atmosphere at an angle. Because of the reduced intensity, the amount of glare will also be reduced, and the Sun can look as if it is shrinking.
Flat-Earthers often see this phenomenon as ‘evidence’ of a receding Sun during a sunset. They are wrong.
Sun glare occurs primarily because of a very intense source of light that is far brighter than objects around it. It can also happen because of scattering in the atmosphere. Sometimes it happens because of internal reflection of the optical system used to capture the scene.
The intensity of sun glare is less than the intensity of the light coming directly from the Sun, but it is still too bright for our eyes to distinguish it. That’s why the Sun and its glare appear as a single bright object.
To observe the Sun without its glare, we have to reduce the exposure. But sometimes even with the camera’s lowest exposure settings, it is not low enough to get the picture of the Sun without glare. To mitigate the problem, we can use a solar filter that can filter out most of the sunlight.
We tried to simulate sun glare using a camera flash attached to a remote trigger. To simulate the sun’s light, the head of the flash is covered by a perforated sheet of thick paper. Glare can be easily replicated if the flash is set bright enough. We can make the glare practically disappear by lowering the exposure by 9EV.