More often than not, we can't control the direction of our light source. We can't control the sun, so we wait until golden hour. We can't move our windows, so we move our subjects.
But we can control the direction of our speedlights, so let's talk about a situation that many beginning photographers might find themselves in: making photos with a speedlight on-camera. This photographer is maybe a little nervous to learn off-camera flash, or maybe this photographer needs to be mobile and can't put a flash off-camera.
For this tutorial, my subject and my camera stayed in the exact same place. I only adjusted the position of my flash and the exposure settings. The following photos are straight-out-of-camera, no adjustments made at all.
Here's how the direction of your on-camera flash (and the direction of your light) will affect your photo.
First, don't point your flash directly at your subject. That will give you a small, harsh light source with flat light. Here's an example:
When looking at a portrait, we always look at the eyes first. Are the eyes illuminated in the photo above? Yes, but everything, including the eyes, just says, "This is a flash photo!" There's nothing natural or inviting about this photo. If that's what you're going for, then fine, but my paying clients would never want this photo.
That means it's time to "bounce" your flash. That's the first skill a new owner of a speedlight should master. Where do you point it? Maybe straight up at the ceiling, right? You'll create a huge light source (the ceiling is bigger than your flash), and the light will come from a "normal" direction, much like the sun or overhead lights. Here's an example:
But look at the eyes again: they just lack life. Plus, I don't like the shadows. The jawline might look okay, but around her eyes there's too much bagginess from the shadow. Why all the problems? Because none of the light came from a horizontal or diagonal direction. Everything came from above, so nothing filled in the area underneath the eyebrows or bottom eyelids. The light was just too vertical.
What's the solution? To get good light when bouncing your flash, point the flash up and over one shoulder. Here's an example:
Now there's light from many directions: vertical, diagonal, and horizontal. Most importantly, more light catches the eyes and more light fills in around the eyes. Overall, it's just a more flattering look.
The direction of your light plays a huge role in two important aspects of a portrait: the shadows and the catchlights in the eyes. Shadows help create shape and dimension. Catchlights give eyes a sense of vitality. You need shadows and catchlights to make a good portrait. Pay attention to the direction of your light to create good shadows and catchlights.