I've been using Indigo for quite some time but I haven't bothered using the exposure controls. I always use the default auto exposure for the camera when rendering scenes.
In real life, I use these exposure settings when taking pictures on my camera. Yesterday I started doing some test renders with different exposure settings to see what the results would be.
default auto exposure
exposure = 0
exposure = 1
The plant model including the bark texture was downloaded from archibase.net. The guy who uploaded it did not mention what kind of plant it is. It looks like a ficus tree so I just assigned a dull plastic preset for the leaf material to make the leaves shiny.