In the real world, we are used to seeing light sources not only at night but during the day as well – even in the daytime we recognize a car has its headlights on for example. Although we can not see the light from such a light source, since daily light from the sun over-lights it, during dawn and dusk we can. E.g. the light from headlights is seen in the morning about an hour after the first rays of the sun. Lit light sources (like car headlights) are evident even throughout a sunny day.
The night was very dark in Arma, which many players appreciated. It was caused by almost zero value of ambient light. However, to avoid overexposing the image at night by artificial light sources (street lamps, car headlights, fireplaces, etc.), the Light Value (LV) of these resources and the intensity of the emissive materials were very low. Therefore, when the sun came up, they immediately ceased to be visible. Twilight in Arma could not have looked like in reality for these reasons.
An example for better understanding:
The sun as light source has a very high light value and it can not be measured by standard means (estimated at 25-30 LV). Meanwhile, its light on a clear day at noon is then 16-18 LV. Car headlights are 19 LV and therefore brighter than sunlight. When lit, they should be seen in the daytime. Their light at a distance of 1 meter has a value of 11 LV, and because it is weaker than sunlight, it wouldn't be apparent at noon.
To approach the situation in the real world, we have increased the intensity of the ambient light at night. The night, however, is still dark, because at the same time we've increased the aperture. The human eye in the real world cannot adapt below a certain threshold and therefore sees darkness with some remnants of light. If we now were to play as a cat in Arma, we would reduce the aperture at night and the night would look brighter.
This change has allowed us to set higher values of lights so that they are seen at dawn and dusk, and the light sources themselves even during the day. The brightness of the lights got closer to their real originals.