Sky images are very useful in render elaboration since they complement lighting.
That is, if you have an image with day-light effect, you will surely use a day-sky image,
and if you have an image with a sunset-light effect, you will surely need a sunset-sky image.
The ies lights are very used as complementary lights in
the production of renders, already be interior or exterior.
They help us to create great effects of punctual lightings,
giving a realistic sensation of the behavior of the light.