Don’t believe what people tell you about training for the Olympics or climbing K2; one of the hardest things you can do is take a good portrait of someone.
Unless you happen to own a photography studio, complete with backdrops and studio lighting, you’ll probably run into all sorts of problems capturing the shot you want. The biggest problem by far? Lighting. Often, your primary light source (the sun) is situated behind the subject and causes your camera to underexpose the subject.
Consider a fairly classic portrait pose: Someone sitting in front of a window. You might want the camera to capture the scene out the window, for example, but that’s likely to significantly underexpose the person. On the other hand, if you base your exposure on the person, you risk blowing out (overexposing) the window.
It’s a tricky shot, but by no means an impossible one.
Here’s the secret: Try to envision the scene the way your camera sees it. Your camera can choose only a single exposure setting, but different parts of the scene have dramatically different lighting levels. So you can expose for the bright light in the window, which will fatally underexpose your subject’s face; or you can base the exposure on the subject’s face, and blow out the window—obliterating the background details you were trying to capture.
The best solution is to add light to the subject to equalize the light in the scene. That way, one exposure will properly capture both the foreground and the background. There are a few ways to do this.
Soft box: I’ll start with my favorite solution: Set up one or two cheap “studio” lights. I can hear you protesting that you aren't a professional, and that you have no need for (or expertise with) studio lights. But you can get a pair of soft-box lights without breaking the bank, and they aren't especially tricky to work with. Soft boxes house a bulb inside a nylon “box” to diffuse the light—sort of like a lantern in a miniature camping tent. A simple setup complete with stand, lamp, and bulb is fairly inexpensive. I use a Westcott 2-Light kit that includes a pair of stands and soft boxes and costs less than $250.
You’ll need to set the camera’s exposure with some care. Set up your shot, position the subject in front of a window, and place any lights that you plan to use in front of the person, to illuminate the face nicely. Then point your camera at the window in Program mode and note the exposure that the camera wants to use.
Next, set the camera to Manual exposure mode and dial in that same setting. This “locks in” the exposure so it won’t change when you point the camera at your subject. Take a photo and review it on the camera’s viewfinder. How does it look? The background will probably looks fine, but your subject might be under- or overexposed, depending on your lights.
Taking your cue from how your test shot came out, move the lights closer or farther away, and try again. With this approach, you can zero in on the proper exposure in just a few shots.
Household lights: What if you don’t want to splurge on lights, or if using them simply isn't practical? Improvise. You can bring a few ordinary household lamps into the room and position them near your subject. Though cheap and easy, that method isn’t ideal: Household lights put out relatively little light, so you’ll need to set them pretty close to your subject. Worse, the lights may have different color temperatures, which could affect the skin tones in the photo.
Fill flash: Finally, don’t forget that you can use your camera’s flash. Set your camera’s flash to 'Fill flash' or 'Forced flash' mode, so that it will fire regardless of how much light the camera thinks is in the scene.
Take a photo and check the result in the camera’s LCD display. If the flash overexposes your subject, check to see whether your camera’s menu system lets you reduce the intensity of the flash. You might be able to drop the flash by one or two stops to fine-tune the effect. That’s how I captured this window portrait.