For a sky with texture, the effect of the Enhance external brightness option depends on the used image.As it turns out, enhancing the external brightness works perfectly with textured skies, in fact it works better than with non-textured skies.
Here are some images showing different versions of the photo plug-in.
Version 1.2 has an option to enhance the external brightness for a sky without texture.
Option disabled (default)
Option enabled
Santbose,
As said Mazoola, Sunflow uses different types of light for a sky without texture (SunSkyLight) and a sky with texture (ImageBasedLight).
Although they have a parameter that seems common, rendering for a sky with texture depends on the image used (example: blue sky or cloudy sky).
Option disabled
Option enabled
