My favorite natural outdoor light is from a rising or setting sun shining under heavy cloud bank. The background will go dark and the subject will pop. This light generally does not last very long, so you need to be ready for it.
On this particular evening, I was testing the AI Server AF capabilities of this lens. Images like this are some of my reward for such work.
Camera and Lens Settings
400mm f/4.0 1/1600s
3456 x 5184px