The Sun has the angular size of approximately 0.53° seen from Earth, and it is practically constant throughout a single day. But sunlight is very intense and result in a glare that surrounds the Sun. Because of the intensity, we are unable to distinguish the Sun from its glare.
During a sunset, the intensity of sunlight is lower due to the fact that sunlight has to traverse Earth’s 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 use this phenomenon as ‘evidence’ of a receding Sun during a sunset. They are wrong.
Sun glare occurs primarily due to a very intense source of light which is far brighter than objects around it. It can also happen because of scattering in the atmosphere. It can also occur because of internal reflections in the optical system used to capture the scene.
The intensity of sun glare is less than the strength of the light coming directly from the Sun, but it is still too bright for our eyes to distinguish it from the sun itself. It is the reason 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 small enough of an exposure to get a picture of the Sun without glare. To solve the problem, we can use a solar filter which can filter out most of the sunlight.
We tried simulating 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 nine stops.