I am often surprised at how many pictures I see that have terrible lighting. More importantly I am often disappointed at how many photographers don't know the difference between good light, bad light, and beautiful light. My experience is that they also have no idea how to change the light. These are usually the photographer that say, "they only shoot available light". I say good luck with that. You'e very limited.
The image above is of a model I shot last week. When I showed up at the park to meet her at 4pm the light was harsh and the trees created a tons of speckled light. Both are terrible to photograph a model in (Trust me, I've learned this the hard way). So what could I do. The model looked great, but the light was terrible. Simple! I changed the light! I pulled out an umbrella, a reflector and a few Nikon speed lights onteh CLS system. I was shocked when she said she'd never seen any of these tools before. I mean she's a model, she should know some of this stuff as well as I do.
I guess that speaks the to level of photographer she's been use to. Using the umbrella and reflectors helped shape the light giving it a warm even feel. It's not harsh or speckled at all. I did put tungsten gel over one speed light to help warm up the light. See, out door lighting in harsh conditions isn't impossible to shoot with, you just have to know how to manipulate the light. (Joe McNally would be so proud of me!)
It's the same with the model below. I recently got a complement that said, "stunning combination of model and natural light!" But that's just it. This isn't natural light. It's another example of a speedlight with a warming gel shooting through an umbrella. It just looks natural. That's the point!
These techniques are just for models. You can use the same ideas at wedding, still life, even journalism. Any place the light isn't great is a place you can make it better.