Taking good outdoor portrait pictures could be really easy or really hard depends on the natural lighting conditions and what we are trying to achieve. When we are lucky enough, the free lighting from the sun is all we need to take good pictures, but more often we are not as lucky, especially from a professional photographer's point of view. Besides other reasons, professionals can't afford to plan our jobs based on best case scenarios. Direct sunlight can cast too harsh a shadow on people's faces, can force people to squint their eyes, and if it's the only light source, can seriously limit people's choices of positioning. So more often than not, we need lighting tools like diffusers, reflectors, and artificial lighting, etc. to achieve a good picture. But on the other hand, with enough preparation, our choices become almost unlimited.
For example, most people new to photography learn to have the subject face the sun so that the face won't be too dark. Well, with flashes to fill in, it's not a bad idea to have the subjects face away from the sun so that the sunlight can serve as the free rim light and it's also easier for the subjects to open their eyes. Here are two examples:
Carrying a lot of lighting gears can be a logistic challenge and can slow us down. So sometimes I only carry the smaller Nikon speedlights. They are powerful enough even during the day if you place them close enough to the subject. But that's not always convenient and sometimes not even a choice. That's when I carry much more powerful studio lights.
In the following experiments, I first shot from a distance of at least 60 ft from the subject who was in the shadow, and with the big light just next to me. It's up to the task. Then I decided to see if the big light can overpower the sun so that it looks like we are shooting during the evening, not for artistic presentation in this case but just to test the power. It did it again easily.
The point is: With the best low light camera money can buy and with a couple of powerful flashes, I can turn evening scenes into days and day scenes into nights. I wonder, with all this new technology, are we going to be limited only by our imaginations soon?