Portrait Lighting

Basic lighting setups haven't changed for over 100 years (or since we could have indoor lighting for photography).  The nice thing about digital is that you can experiment to your hearts content, seeing the results immediately, but the first thing you'll learn eventually are these standard lighting concepts:

You need a key, or main light, which is just what it sounds.  It provides the primary light source for your image, and should be the only one which shows definite shadows (if you have more than one shadow source in your image it will look confusing and amateurish). 

You usually need a fill light, which simply reduces the contrast between the main light and the shadow areas of your image.  This light is never brighter than your key (or it would be the key) and is usually not as bright (or you would have flat light).

You may or may not have a hair or accent light.  This light, aimed from the back, lights the back of the head to provide separation of the head from the background.  It's pretty trite nowadays to have such a light, but it has become a cliché because it's effective.

You may or may not have a background light, which lights the background (duh).  You'll need this if your background needs to be lit (you don't want a dark or black background) and your key and fill lights do not provide enough light (they usually won't).

So at the very most you'll need four light sources, but usually you can work just fine with two or three (and sometimes you can get by with one).  Also note that reflectors and/or natural sources (like the light from a window) can substitute for one or more of these lights.  So if you only have one flash you can still produce nice portraits (it just requires a little more effort).

How they work

Let's see these lights in action.  First we'll discuss how to place our key, or main light.  Usually you'll want to position this high, high enough that the shadow cast by the nose comes down to just touch the upper lip (however, you don't need to put it this high if room and/or your lighting stands don't permit it).

The next issue is where, to the side, you want to put the light.  There are three distinct places -- directly in front of the model, to the short side and to the long side of her face.

Placing the light directly in front of the model gives you much the same kind of lighting you would get if the flash were mounted on the camera.  The only difference is the light is a lot higher, so we see shadows coming down, but the light itself is pretty harsh and unattractive to the face.  We'll discuss how we can use this light later on.

Placing the light so that it illuminates the broad side of the model's face is even worse in most cases.  It's the usual mistake a beginner makes in portrait photography.  The problem is that with the light on this side of the face it makes the model's face look wider, which is not usually what you want to do.  Unless your model is Calista Flockhart it's not recommended to use broad lighting.

The third option is placing the light so it illuminates the short side, or the side of the face away from the camera.  This is called, naturally enough, short lighting, and is by far the preferred lighting of portrait photography.  It makes the face slender and is very flattering for nearly everybody.  Note that the model faces the light, turning her face slightly away from the camera (for a real person have him or her look with their eyes at the camera as their face is turned away).

Now that we have our key light placed, the only thing that remains is to fill in the shadows to our liking.  Traditionally the fill is mounted behind and above the camera position.  If you are using the EOS wireless flash system you can set the ratio between your fill and key lights quite easily. Here are two typical ratios: 

If you want a hair or accent light you can add one behind the model, pointing at the top of their head.  You must be careful that this light does not shine into the camera, nor do you want it to illuminate anything other than the hair.  Studio lighting systems use barn doors (devices which fit over the lights to limit where they shine -- they look just like the doors on a barn) to control just where the light will go.  Done correctly the light does add a nice touch, although some folks (like myself) feel it's a little artificial looking.  In order to see what this looks like we need to see a subject with dark hair, as our blonde already stands out from the background.

The only other thing that remains is to light your background.  If your subject is quite close to the background your key and fill lights may do a good enough job.  Otherwise, a dedicated light aimed at the backdrop will fill it out nicely.

But softly

Once you have the basic concepts down you are free to break the rules as needed.  We mentioned that light shining directly into your model's face -- if you can diffuse the light enough you can end up with one of the most flattering of all portrait shots.  This requires a lot of diffusion, because you want to eliminate nearly all shadows, and you need the light to "mold" around the model's face to keep her from looking as fat as Louie Anderson.  Shooting through a white umbrella will do the trick, as will the various softboxes and moon lights available.  

If you only have one flash and you need to keep it on camera you can buy the devices by Lumiquest to soften your flash output.  These are the "poor man's" umbrellas, and while they will do in a pinch they are no substitute for using umbrellas and real soft boxes.  If I have to use on-camera flash (like at a party where I'm just doing candids and available light isn't an option) I use these.  They are also good for softening fill flash outdoors, where the sun is your key light.  

And if you are in a situation where you only have the one umbrella and/or one light stand, if you have the 550EX you can put it on the camera as both your fill light and your trigger for your other flash mounted on the stand.  Use the Lumiquest stuff to soften your fill and you have a little "mini-studio" that's easier to work in crowded rooms (used this way don't forget to reverse your 550EX ratios so that the on-board 550 is set for lower output than your stand mounted key light flash).

Finally there are all the wonderful things you can do with putting various colored gels or filters on your flash units.  Lumiquest makes a gel holder, complete with gels, that allows you to get very creative.  As a rule you'll want to use these only on your accent and/or background lights but if you want to go wild there's no one stopping you.  If you are tempted to put gels on your key and fill lights, remember a rule of thumb from theater is to mix both "hot" and "cold", so that you might have a warm gold light as your key, and a cool blue light as your fill.  Mixing colored lights like this may not prove flattering to your models, but it might win you awards.