In studio photography, just as you can control the subject matter, so you can control the intensity of the lighting by changing the lighting itself. In outdoor photography that isn’t possible, but you can still use lighting to help compose your photos. One way to do this is to select the time of day or weather conditions under which you take the photos. You will achieve a dimmer, more diffuse light on an overcast day than you will under bright sunshine. Also, different lighting conditions prevail at night, under artificial light (or moonlight) than in daylight.
The other way to control lighting outdoors is to start from the other end. By adjusting the aperture, shutter speed, and ISO sensitivity of your camera, you can increase or reduce the amount of light entering the camera and so make the picture brighter or dimmer. This can be used to overexpose or underexpose the photo deliberately. Overexposing the photo gives it a more “washed out” appearance, bringing up detail in things that are in shadow that might not be shown in a “correctly” exposed picture. Deliberately underexposing it on the other hand deepens the colors and shades in brighter parts of the picture, at the cost of making the dimmer parts even less visible. Besides deliberate over-or under-exposure, you can use your control of the three factors behind exposure (ISO sensitivity, shutter speed, and aperture) to take pictures in very dim light that appear as if they were taken in somewhat brighter light. This can allow nighttime photography without the use of flashbulbs or electronic flash. As you take more pictures, you’ll get a better feel for what your camera can do in terms of exposure and what changing each of the exposure-relevant variables Keeping these rules in mind will let you adjust light sensitivity in the way that will produce the effects you want. Here are some other rules of thumb that will help you in controlling the lighting conditions either outdoors or in the studio. The broader the light source, the softer will be the light. Conversely, with a narrow light source, you get a crisp, sharp light. A broad light source softens shadows and contrasts and lowers textures. That’s because a broad light source allows light to hit the subject from multiple directions. In portrait photography, for example, a soft effect can be achieved by positioning the subject near a large window that does not have direct sunlight exposure. The more distant the light source, the harder the light. This is actually a variation on the above rule. If you position a light source closer to the subject, it will be larger relative to the size of the subject. If it’s shining from a distance, it’s more a single-direction light source that sharpens contrasts and shadows. You can use this rule to create the most flattering images (or the most creative and desirable ones) in indoor photography. Diffusion scatters light and makes for softer lighting. Diffusion refers to light shining through a translucent substance, such as clouds, fog, or filters and screens. A picture taken outdoors on an overcast day or in a fog will be softer in effect than one taken on a sunny day. The same principle can be used indoors through the use of filters and screens to create a diffused light and produce a softening effect. You can make your own filters using materials such as white cloth or translucent plastic. Outdoors, you can use a light tent or canopy to diffuse the sunlight in the absence of any natural clouds or fog. Bouncing light diffuses it. If you shine your light source not directly on the subject but rather on a matte surface such as a white wall or a matte reflector, a softer quality of light will be produced. Note that this really only works with a matte reflector. If you use a shiny reflector, such as a mirror or a piece of polished metal (something you can see your reflection in), the light will remain almost as sharp as if it were used directly. The more distant the light source, the more it weakens. This is a pretty obvious one. A light source is stronger and brighter when it’s closer to the subject of your photograph, and weaker and dimmer when it’s further away. There’s a mathematical principle called the “inverse square law” that governs this, which says that light varies inversely as the square of the distance from the source. That means when the source of light is twice as far away, it’s four times weaker. When it’s three times as far away, it’s none times weaker. Just remember that when a light source is farther away, it becomes sharper, but also weaker, and adjust your expectations accordingly. The closer the light source is to the subject, the sharper will be the falloff of light on objects in the picture further away from the light than the subject. When you shine a light from a short distance on something in the foreground, the light is much dimmer (in proportion) on anything a bit further away from the light than the subject is. For example, if you photograph a person with a bright light shining on his face from a short distance, the light on anything behind him (due to the inverse square law) will be dimmer. Because you set your shutter speed and/or aperture based on the light on the subject, the other objects in the picture can appear to be dimly lit. If the light is further away, the difference between the lighting on the foreground and background will be less, and the whole picture will seem more evenly lit. You can use this tip to control how much background shows up in the picture. Lighting from the front softens texture. Light from the side, above, or below sharpens it. If the light is coming straight on from the front, the details and textures in the picture will be softened. This is often a good thing for portrait photography as it can soften imperfections. If you want the textures of your subject sharply defined in the picture, arrange it so the light comes in from the side or from above or below. (Of course, each of these will also make a difference in terms of shadows cast and other variations.)Shadows generate a sense of volume. When shadows are sharply defined, they create a three-dimensional feel to the photograph (which is, of course, a two dimensional image). Several of the lighting tips above can be used to deepen shadows when a three-dimensional feel and sense of volume are desired. For example, using side lighting or angular lighting can deepen shadows and thus create volume. Backlighting creates highly diffuse lighting, but makes for difficult light metering. When most of the light source is from the back, the reflected light off a surface in front of the subject (such as a wall) can provide very soft, diffuse lighting. If the light source itself is in the photo, this can create some very interesting effects such as silhouettes, but you have to be careful when using your light meter. This creates what’s called a “high dynamic range” (HDR) lighting situation and requires a technique called “exposure bracketing.” Exposure bracketing involves taking three different shots, one exposed exactly as the meter says, one about one-third underexposed, and the last about one-third overexposed, to compensate for errors that may arise when sampling in high variable light fields. Even light your eye sees as white has color to it. The color of apparently white light is called color temperature. Our eyes and brain adjust our natural perception so that we don’t notice this variation much, but a camera does not. That’s one reason why the image taken by your camera may not perfectly match what you see with your eyes. Sunlight in the early morning and late afternoon, not long after sunrise or before sunset, can generate a warm-color cast to the picture. Bright noonday sun, on the other hand, gives the photo a bluish, cool color tone. Your digital camera has a white-balance control that lets you shift this color balance either to compensate and neutralize the color temperature or to emphasize it for deliberate effect. One use of this feature involves landscape photography. On a clear, bright day, a landscape photo can be strongly blue shifted in appearance. If you set your camera’s color balance to “cloudy,” you can compensate for this and give your photo a warm glow.