So I'm going to start our discussion of studio photography by noting that studio photography is not for everyone. Some photographers just don't want to invest in a studio light kit, others can't afford it. Still others just find the whole process of setting up, breaking down and making minor adjustments to studio lights and portrait backdrops to be somewhat stifling, especially on a creative level. While some photographers thrive in a controlled studio setting, there's nothing wrong with taking the opposite approach. So if you think you might fall into more of the natural light camp, there's nothing wrong with that. I do encourage you to try out studio lighting techniques, though, just to see if you've misjudged you own proclivity for using them, but in the meantime there really is nothing wrong with natural light portraiture. So let's discuss natural light portraiture before we move on to the studio itself.
The sun is the brightest light on Earth, and it makes an absolutely beautiful portrait lighting set up under the right conditions. With the operative phrase being, of course, "the right conditions."
The sun at midday
If you've ever tried to shoot a portrait outdoors under the midday sun, you know exactly what I'm talking about. Midday sun is not the ideal kind of light even though it can be qualified as "natural." Midday sun casts ugly shadows in all the wrong places, for example, in eye sockets, under noses and under chins. Hat wearing subjects are particularly vulnerable to the horrors of midday sun--you may lose entire faces beneath the shadows cast by broad-rimmed hats or baseball caps. For this reason, it's often better to just avoid shooting in midday lighting conditions altogether, if you have that option. Instead, schedule your photo shoots for the early hours of the day or the late hours of the afternoon. This is the time of day we like to call the "golden hour," when the sun is low in the sky, the light is naturally soft and golden and just more flattering for portrait subjects overall.
If you don't have a choice about what time you find yourself trying to capture flattering portraits of your friends and family, there are a few things that you can do to improve the quality of those midday images. First of all, you can just move the entire group (or individual subject) into open shade. This is a great idea if you have a nice large area of shade, that is, if you are not under a tree where the light is dappled or patchy. Open shade is much more even, and although it tends to produce images that can be on the flat side, this can be easily adjusted for in post-processing after the fact.
DSC08312 by Flickr user austin.connell
You can also improve your midday portraits with use of fill flash or a reflector. Fill flash is simply a way of adding light to the shadows, thus making them less extreme. You can use your pop-up or onboard flash as a fill flash in a pinch, however, onboard flash is not very bright, so it has limited range. It is also direct, which means that it might flatten your subject out a little and erase fine detail, so you may not get completely satisfying results if you use one. For better results, use an off-camera flash, and hold it to one side of your subject so that you will get a more three-dimensional looking image. A flash held off to one side will produce an image that is has a highlight side and a shadow side, which will flatter most portrait subjects.
A reflector is an alternate way of adding light to the shadows, and it can be a lot more versatile than fill flash because you can see what it's doing to the shadows before you make the exposure. The problem with reflectors is that they can be very large and visible, so you have to have someone present who can hold and adjust them for you, whether it's the subject himself or an assistant. Reflectors are typically sold in sets that include a white side, a silver side, and a gold side—for bright, sunny days you want to rely mostly on the white side — the silver side can be overly harsh in bright light and is best used on overcast days when you need a little extra boost. The gold side will simulate golden hour light and add warm tones to the photo, but again this can be a little harsh on a bright sunny day. Alternately, you can use a diffuser, which is usually included with your set of reflectors—the diffuser is different then a reflector in that it actually diffuses the light before it hits your subject rather than bouncing light back into the shadows. To use a diffuser, you simply need to place it between the light source—the sun—and your subject.
The golden hour
Ultimately, shooting portraits at midday is not ideal, and you should avoid having to do it if at all possible. Instead, shoot during the golden hour, which will give you soft, even light as well as a golden color that will compliment almost any skin tone. For the most flattering look, orient your subject so that the sun is either on the left or right side--again, that helps your image appear more three dimensional. You can also place the sun in front of your subject if you want to deemphasize certain features such as wrinkles or blemishes.
Another great way to use natural light to your advantage is it to shoot with window light. The beautiful thing about window light is that you can use it no matter what time of the day it is, provided that the window has good sun exposure, the sun is bright enough and is not shining directly through the window. Window light is naturally soft and diffused, and you can make it even more soft and diffused by placing a diffuser or even a sheer curtain between the glass and your subject. And window light is side light, which means you're naturally going to get that three-dimensional look that is so flattering for almost anyone.
You can adjust the brightness of window light by simply moving your subject closer to or further away from it. For a dramatic look, use the window as your only light source. If you want a little less drama, use a reflector to fill in some of those dark shadows on the non-window side of the face, or try opening doors and windows to let in more ambient light. You can also turn on some of the artificial lights in the room, but be aware that when you combine different types of light you may have some issues with white balance, depending on the types of bulb you use in those artificial lights. Some artificial lights are incandescent, which may cause a yellow cast. If this happens, you can convert your image to black and white to eliminate that color cast altogether, or you can set a custom white balance using a photographer's white card or other true-white surface.
If you want to change the direction of the light you simply change the position of your subject. This makes window light infinitely easy to control, and you don't need to make any adjustments to the light itself. You can even use window light as front light—simply place yourself between the window and your subject and have your subject face the window directly. Again, this is best used if the subject has blemishes or wrinkles that you would like to reduce the look of--this lighting direction tends to flatten out unflattering features on the subject's face, but also has the effect of flattening the image over all, so keep this in mind when you choose to shoot using front light. You can also backlight your subject by placing him directly in front of the window--use spot metering on your subject's face to make sure you get the exposure right (you may have to add or subtract a little exposure compensation depending on your subject's skin tone). A good back-lit portrait will have a well exposed subject, but the window itself will be a little blown out. Alternately you can choose to spot meter the window, which will give you a nice, well-exposed window and a silhouetted subject.
Window light is abundant and free--you don't need to set it up or break it down again, and you don't need to make a big investment in lighting kits and future investments in bulbs. Natural light can give you excellent results, and you could easily get through an entire career as a portrait photographer without ever setting up a studio light. Of course, this isn't going to make you the most versatile portrait photographer around, so it would behoove you to understand studio lighting as well, because in understanding studio lighting can give you insight into the science an application of lighting techniques in general, which can even improve the quality of photographs shot with natural light alone. So once you've mastered natural light portraiture, it's time to move on to that indoor stuff you may have been avoiding all of this time. Even if it doesn't turn out to be your favorite way of shooting portraits, understanding studio lighting will make you a more well-rounded photographer overall, even when you're shooting natural light portraits.