Shooting outdoor portraits and in the open, you really have two basic ways to use the ambient light. Either shoot front lit, meaning, the light hits the subject from front, or shoot backlit, in which case the subject is lit from behind. Front lit scenes are usually brighter and more contrasty than backlit scenes, but you also run the risk of your images getting washed out. This means details can often be lost due to the harsh reflections. Plus, if you are shooting portraits you are likely to find your subjects squinting. There is also a likelihood of big shadows under the eyes, neck and nose. Backlit scenes are more uniform.
You don’t always have to shoot at the golden hour in order to use this technique. Simply asking the subject to stand with her back facing the sun (while it is slightly at an angle) can very well achieve great portrait lighting. Sometimes this technique is accentuated with a little bit of fill-light using a white foam board.
Backlit scenes will allow you to meter properly for a scene. This is because you are metering for the shadow, which is stable. No matter how bright the background is the exposure value for the shadow area will remain somewhat stable throughout the session. That also means you wouldn’t have to continuously change back and forth between different exposure values.
Rim Lighting Effect
In lighting we often use a specific type of arrangement that is known as rim light. Rim light is a light that is placed beside or at the back of the subject that illuminates the edges of the subject’s head, shoulders and the torso. Seen the ‘halo’ effect on some portrait images when shot at the golden hour? That’s rim lighting in action. This is only possible when shooting backlit.
When you shoot against the sun it helps you to separate the subject from the background. Yes, you could also shoot with a wide aperture and get what is known as shallow depth of field, but you will lose the background in the process. By keeping the sun behind the subject you get both the background (if it is interesting) as well as achieve subject separation.
Effects of uniform lighting on the tone of a portrait
I spoke about uniform lighting in the opening paragraph. One way to create a flattering portrait is to use uniform lighting. What is uniform lighting? Any lighting that does not create harsh shadows is a uniform light. A strobe fired against an umbrella, a flash fired within a softbox, or even shooting against the sun are examples of uniform light. For less flattering portraits fire the light from the side and create a brightly lit side as well as a shadow side. Uniform lighting will hide skin blemishes creating a smoother look.
One effect of putting the sun behind the subject and in effect achieving uniform light is less contrast. Less contrast again is more subtle and flattering for portraits than high contrast front lighting.