Camera Flash Tutorial (Part 3: Key Lighting)

For part 2 go here: http://saritsblog.blogspot.com/2014/12/camera-flash-tutorial-part-2-theory.html

In our last tutorial, we talked about moving your flash away from the camera, but we never talked about exactly where to put it. Knowing where to put and point your lights is where your technique and creativity takes shape.

More Terminology
When it comes to lighting, it helps to know about 3 basic types of light and what effect they provide in the scene:

1. Key Light - These are the main lights used to "produce" the shadows. If we remember from the previous tutorial, we need to make sure the key light points in a direction that is different from the direction our camera is pointing at.
2. Fill Light - Since the key light's goal is to define the shadows, sometimes those shadows become too dark to make a properly exposed photo. The goal of the fill light is to bring just enough light to the dark areas to show what's in shadow without blowing away the shadow itself.
3. Rim/Hair/Kicker Light - Sometimes the background of the scene blends into the subject you are focusing on. Think of a black haired singer on stage in front of a black curtain. It would be hard for viewers to tell where his/her hair ended and where the curtain begins. The rim light's goal is to define the edges between the subject and the background. In the case of hair, this can be done with the light behind and above the subject point down onto the head.

Types of Key Lighting

1. Regular or just Key Lighting - Just use light your subject to get the right exposure. Most of the time you will be doing this. Typically, a light coming 45 degrees from the left or right is a good starting point. The more perpendicular this light is to the camera the longer the shadows will be which creates a more striking and dramatic the look. The closer to the camera the more even lighting will be. This is often best for beauty shots where you want the skin to look more smooth and even.
2. Low Key Lighting - "Low" in this case simply means dim. This provides a very dramatic look. The key to taking this photo is to use enough light to properly expose a portion of the subject and design the lighting so that it falls off rapidly everywhere else. As you can see in the photo to the right, the girls face is well exposed but the light quickly diminishes over the rest of her body.



Low Key Lighting - Photo by Bonita Suraputra
https://creativecommons.org/licenses/by/2.0/

3. High Key Lighting -  Here we increase the light or exposure until things seem overexposed. This creates a more light ethereal feel. Shadows are 

   

   High Key Lighting - Photo by https://www.flickr.com/photos/ribenawrath/
   https://creativecommons.org/licenses/by-sa/2.0/

Fill Light

Often times after key lighting, the shadows end up being too dark so we need to use some fill lighting to lighten them up. Remember how using on camera flash eliminates shadows? This is the perfect time to use your on-camera flash to lighten shadows. By adjusting the Flash Exposure Compensation (FEC) you can dial-in exactly how much you want the shadows lightened. This is particularly useful in direct sunlight photos as you can see below. Because the girl is being backlit by the sun, her face would have been completely dark just like the shadows you see on the stairs. The fill flash is just powerful enough to show the details while letting the sun do most of the work.

Fill flash used to brighten the face. Notice how dark the shadows are on the stairs.

You can even use the sun as both the key and fill lights by using a reflector as show below.

Using a reflector to provide fill light - Photo by Peter McConnochie
https://creativecommons.org/licenses/by/2.0/

Rim/Hair Light

Lastly, separating the subject from the background is easily accomplished by placing the light directly behind and/or directly to the side perpendicular to the direction the camera is shooting depending on the effect desired. This type of lighting creates a great effect on anything with hair like this teddy bear for instance.

Rim light separates bear from background - Photo by Nomadic Lass
https://creativecommons.org/licenses/by-sa/2.0/

Kicker
Kickers are technically different from rim lights but their use and effect are close enough that I've grouped them together. The goal here isn't to create a silhouette, but to give some highlights or a "kick" on the side of the subject. Using kickers can be tricky and usually requires an artificial light to get the right placement and control to produce pleasing results so I recommend holding off on using them until you've mastered the other lights.

Putting it all together

Now that we understand the different types of light we can use in our scene, its time to formulate a lighting strategy that you can apply to any scene.
Here's my strategy:

1. Identify all the sources of light - This can be sunlight, reflectors, flash, candlelight, street lamps, neon signs, etc. See what kinds of light you can and cannot change. Sometimes using the light that's already there can be much easier than trying to illuminate everything yourself. It also tends to look more natural if you can use existing lighting instead of trying to overpower it with your flashes.
2. Compose your scene - Pick your subject/foreground/background and pay attention to how the light is reacting. Try to expose your scene for the elements that you cannot control, like a sunlit building in the background. You can then adjust the light output of the things you can control to get the correct exposure for everything else.
3. Decide if you need fill lighting - If one side is in shadow, see if moving around causes other lights to form rim/hair lights. Rim lighting can sometimes take the place of fill lighting if the outline provides the necessary visual interest. If you need to add fill light, see what you can use, be it flash, reflector, or someone with a flashlight. 
4. Decide if you have enough key lighting - If the subject lacks definition or appears flat, try adding some sort of key light or try increasing whats there by adding a flash firing in the same direction. Since you use key lighting to produce shadows, you can increase the effect of key lighting by reducing fill lighting to some extent. Try covering up or blocking lights that are throwing too much fill light into your scene.
5. Decide if you need rim/hair lights - If you still have some available light sources to do rim lighting and its not too inconvenient , I say give it a shot, always. Sometimes you won't want it for dark, moody pictures but for the most part it generally looks good on everything else.
6. Take your photo - Hopefully, after going through these steps and examining your photo, you'll instinctively know what tweaks need to be made to get exactly what you want in your shot.

Wait there's more...

For completeness sake there are also background lights which you can guess are there to illuminate the background. You typically won't use these unless you have a background small enough or enough lights to adequately illuminate it. If you set your exposure for the background first, you can usually avoid them.