Aesthetic choices. Do you think those photographers left those trees in dark shadows because they wanted or because they could not do otherwise?
They could not do otherwise *cheaply*.
As the sun is *behind* the trees *and* the model, and the trees are far away, I see no *cheap* way a photographer could have pushed as much -in fact more- light into the backlit shadow below the far trees and the backlit tree branches as onto the close by freestanding model.
Let me clarify here: The trees are dark not because the flash is overpowering the sun, but because they are backlit by the sun. Where the trees are, the sun is the light source. Take a flash meter under the trees, and it won't even register the flash.
There is such a thing as the square distance law, and it is very hard to light stuff which is far away. Unless it was "Cooter" or Annie, and a truckful of lights could be set up below the trees. On the other hand, five minutes of retouch may recover some tree shadow and branch detail if the sensor has enough DR.
BTW, this is exactly the reason why the cinema guys and really big shoots travel with tons of large heavy light equipment. They can and routinely do what your average photographer cannot - set up lights on far backgrounds.
I don't have any issues with this nicely done image - just don't tell me that those shadows under the trees could have been easily lit out for a camera with low DR like the 10-bit dSLRs we were all using 10 years ago, or the slide film we had earlier.
Photographer came, balanced backlit brown model body against blue complementary color sky with fill flash, got a nicely composed and colorful image, walked away. Trees and background were collateral damage
Last not least, I have zero experience and competence here; as an "amateur", I own one single flash shaper, a 6 foot Elinchrom Octabank, which I pull out once a year when I have to, and have done less than 20 flash shoots in my life, although I sometimes do video lighting. But any photographic amateur needs to be able to read the light in a scene, and the level of the discussion participants has at this point sunk so low that I feel as entitled as anyone else to participate. ...
Edmund