Light is the single most essential component of photography. Unfortunately, controlling light is complicated and not completely intuitive. The following tutorial will introduce you to some basic lighting techniques that can be used on a variety of subjects and locations to achieve professional results.
It's important to note that the samples below were produced in a controlled environment. When shooting on location or outdoors, you will have many more factors to deal with: lights bouncing off of ceilings and walls, direct sunlight, varying light colors, etc. Knowing the basics will help you in those situations as well, so we'll start at the beginning.
The Key Light
The most important light in your setup is the key light. It's the first light you setup and will control exposure for your image. In this example, the key light has been positioned left of the camera and about two feet higher than the subject, pointing down slightly.
The position of the key light will have a huge effect on the overall feel of your image. Sometimes moving the light a mere 12 inches will change the style of your image completely.
In the example above, having the key light very close to the camera (and a little bit higher than the camera) bathes the subject in direct light. We can see detail across the entire face. Shadows are mostly eliminated, which causes the image to appear somewhat flat. This is a standard light position for news reports and documentary videography, where it's more important to see the entire subject than it is to create a dramatic atmosphere.
The key light has been moved slightly to the left, and the result is clearly noticeable. The left side of the face is brighter, leaving the right side in shadows. The subject appears more three-dimensional.
Imagine a large clock overlaying the studio area if you were to look down on it from above. In the example above, the key light has been moved to 9 o'clock, which is directly to the side of our subject. This is one of the most dramatic positions for the key light, mostly because it produces a very high level of lighting contrast.
Lighting contrast is an important concept to understand. It refers to the difference in brightness between the light and dark sides of the subject. Having extreme contrast like we have in the example above is referred to as low-key lighting. The opposite, where the entire subject is bathed in even light (having a low lighting contrast), is referred to as high-key lighting. Good luck remembering the terms - I have yet to come up with a convention that helps me remember that "low" key has a "high" contrast.
Here the key light has been moved to about 8 o'clock. It's positioned so that some light falls over the bridge of our subject's nose and creates a triangle of light on the shadowed side of her face. This triangle is what I usually aim for when setting up the key light.
Being happy with the position of the key light, let's turn our attention to the shadows that it creates. The nose, chin and eyebrow leave sharp and harsh shadows on the subject. While it's sometimes an intentional choice to have harsh shadows, softening the light typically creates much more artistically appealing images (and can help skin appear very smooth).
So how do we soften the shadows? Easy - enlarge your light source. The larger the light source, the softer the shadows.
Well ok, you can't make your light bigger. One solution is to put a photographic umbrella in front of your light. Umbrellas are cheap and very easy to work with. The umbrella will effectively enlarge the light source, diffusing the light.
In the above photo, an umbrella has been added to the key light to soften the shadows. Notice how much softer the shadows on the face have become. If a soft box light is available, the light source would be larger, producing even softer shadows.
One thing to note is that in the process of diffusing the key light, the umbrella causes a lot of light to scatter, resulting in less light hitting your subject. You will have to adjust your camera's exposure to compensate for the lost light.
The Fill Light
One problem with using only a key light is that the shadowed side of a person's face is very dark, sometimes completely black. It's usually desirable to fill in the shadows a little bit so that you can see the whole face. Hence the name of our next light: the fill light.
In the photo above, a fill light has been placed on the opposite side of the camera as the key light. As expected, both sides of the face are now evenly lit.
But we're not done yet. Having the whole face lit with perfect symmetry negates the dramatic feel of our setup when there was just the key light. Even though we can see the whole face, it's just not as appealing.
Ah, that's better! The change here is subtle but very important. The fill light has been moved farther away. When you move a light back, it casts much less light on your subject. Many times you only need to move a light 5-10 feet away to make a large difference.
In my example above, I have actually used a fill light that is much less bright than the key light. This enables me to have the key and fill light fairly close to the subject, which is essential when working in small locations.
The Back Light
Finally we meet the third and last light in a three-point light setup: the back light (sometimes called the hair or rim light). As you can see above, this light has added a rim of light on the head and shoulders of our subject. Although it's a very subtle change, it dramatically helps visually separate the subject from the background. Instead of the top of her head fading into the black background, now there's a pleasing highlight on her hair and shoulders.
Even though the back light produces little change to the overall image, it's a minor touch that will usually make photos and videos appear to be professionally lit.
The key and fill lights have been turned off, letting us see exactly what effect the back light has on our subject.
Above is the result of using the back and fill lights. Notice that the fill light does not provide full illumination to our subject's face. It's also best practice to use soft fill and back lights whenever possible.
The White Backdrop
Now that our subject is properly lit, we can experiment with the backdrop. Let's try to achieve a popular backdrop, which is a solid bright-white backdrop, free of shadows and detail.
A white sheet has been hung on the wall about 6 feet behind our subject, but we can obviously see that it's a sheet (and in need of a good iron!). Not very professional.
Why doesn't the sheet look white? The reason is that the camera's exposure has been set according to the subject, who is much more brightly lit than the backdrop. Simply put: we need more light on the backdrop.
A backdrop light has been placed behind and to the side of our subject, pointing at the white sheet. It lights up half of the sheet, but we're not quite there yet.
Ah-ha! Two lights did the trick - one on each side. It's important to note that the lights have been positioned in such a way so that their light does not spill onto our subject. Remember - she has been properly lit, and we don't want extra light ruining our setup. There are devices called barn doors which can be put on lights to prevent extra light from spilling in undesired directions. In this case, it was sufficient to just put the lights low on the floor behind our subject and point them at the wall.
The last thing we're going to look at is what difference the vertical position of a light makes to our image. In the photo above, the light is higher than our subject, pointing down slightly. This will almost always produce desirable results. Elevating the light also helps eliminate reflections and glare on eyeglasses.
Now the light has been lowered so that it's the same height as our subject's face. You can see that this produces a much different effect, which sometimes can be desirable, depending on the mood you're aiming for.
The light has been lowered to knee-level, and it has also been moved from an 8 o'clock position to the 7 o'clock position. This produces an eerie effect on the subject, usually desirable in dramatic or suspenseful scenes. This effect can be greatly accentuated by removing the umbrella and lowering the back and fill lights, producing a more low-key image.
That's the end of our basic lighting tutorial. There's plenty more though — we haven't even touched on bounce lighting, color temperatures, gels, cookies, snoots, lens flares, bulb types, silhouttes, set lighting... the list goes on and on.
We'll save that for another day. For now, go play with some lights!