It’s a bit dry in prose, however, I needed to post this somewhere.
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Lighting
Lighting is perhaps the most important consideration when taking a photograph. The lighting on the subject or scene in front of the camera, besides, is the only thing that can produce a photograph.
All light comes from light sources. Natural light is light that comes from the sun, whether directly, or reflected off of and diffused through clouds, windows, and objects. Artificial light is any other man-made light; bulbs, fluorescent lamps, fire, flash units, lasers, LEDs, and so on. The list of products man has developed to light up with world seems nearly limitless.
A light is defined by four qualities. First its strength, which is the amount of light that comes from the light source. Next is the diffusion, or how much the light spreads. This is also known as the “softness” of the light. The direction of the light is the next consideration, and then lastly the tone or color balance of the light.
The strength of the light is easily thought of as how “bright” the light is. On a cloudless day, the sun is usually a very strong light source. Reflected natural light, such as in shade, is much less strong. Artificial light sources are their strongest when placed close to the subject. As the light source is moved away, the strength diminishes.
[Sunny 16 Rule: Note that the brightness of the sun is always about the same. In the grand scale of things, everything is about the same distance away from the sun. So on a sunny day there is always about the same amount of direct sunlight, no matter where you are. The Sunny 16 rule is an approximate correct exposure for direct sunlight: f/16, ISO 100, Shutter 1/125. Adjust to equivalent exposures as needed.]
With stronger light sources, smaller apertures and/or faster shutter speeds are possible. The strength of the light source is the primary consideration for exposure settings. The strength of the light, however, actually has no effect on the qualities of the light, as long as the right amount of exposure is used. For example, if your light source is a light bulb, dimming the bulb and then shooting a longer exposure will, for the most part, produce a photo identical to a bright bulb with a shorter exposure. Balancing the strength of multiple light sources will change the tonal qualities of an image, however, and that will be discussed shortly later.
Diffusion, or spread, of light affects how evenly a particular light source spreads light. The best way to think about diffusion is in terms of shadow quality. A “hard” light source will create sharp, defined, dark shadows. A “soft” light source will create fuzzier shadows with more light filling in the shadow areas. The softest light sources may not have any shadows at all. A good way to picture this is the difference between a bright, sunny day, and a very cloudy day. The sun is a very hard light source that produces sharps shadows and high contrast. When it is very overcast, though, the light evens out, and you may have no shadows at all.
Diffusion of light is essentially a function of how large the light source is. A small, direct light source will give hard shadows, while diffusion will increase with the size of the light source. The sun is a very small light source in the sky, and is very far away, so its light is very direct and hard. On an overcast day, the sun’s rays spread out over the clouds before it reaches the ground, and so the entire sky may turn into a single light source, spreading the light out evenly over the ground. With artificial light sources, a lightbulb or flashbulb is usually used as a small, direct source of hard light. Using a softbox or umbrella, or simply by reflecting the light from the bulb off a surface, however, increases the size of the light source, softening the light. Moving an artificial light source away from the subject also tends to soften the light.
The direction of the light affects the shadowing of the objects in the frame. Shadows give the frame depth and texture. The general lighting directions are as follows:
-Top Lighting: This is when the light source is directly above the subject, like when the sun is at high noon. Shadows are short, and fall directly below all objects. In portraits, this can produce shadows on the eyes, and dark areas beneath the nose and lips.
-Side Lighting: This is when the light source is directly to the left or right of the subject, or when the sun is very low in the sky, early mornings or late afternoons. Side lighting emphasizes texture, and objects show their topography and surface qualities with deep, long lateral shadows. In portraits, this tends to evenly light half the face, casting the other half into shadow. It emphasizes facial features.
-High Side Lighting: This is a special case when the light source is above the subject, but at an angle pointing down at the subject. This is generally regarded as the most flattering direction for portrait light, as it is very natural, imitating the direction of most natural light, and can show detail in facial features without casting harsh, awkward shadows.
-Front Lighting: This is when the light source is directly in front of the subject, usually seen in terms of on-camera flash units. This has a tendancy to eliminate shadowing and flatten out features. While hard, direct on-camera flash light is usually discouraged for portraits for its flattening effects, a popular front lighting technique for portraits involves a ring light, which is an O shaped light through which the camera lens is placed in the center. This provides a much more diffused look to the light.
-Back Lighting: This is when the light source is placed behind the subject. This blocks most of the light from the light source from getting to the camera, but creates a distinct halo of light around the subject. This is also known as rim-lighting, or in the case of portraits, hair-lighting. This often is used in conjunction with other lights to provide some seperation on the edges of the subject from the background.
-Bottom Lighting: This is when the subject is lit from any angle below the angle of the camera. This is the most seemingly unnatural direction of light, as natural light rarely comes from the ground. Shadows go upward, and this method of lighting has a distinctly artificial feel.
When using multiple light sources, the effect is always additive. Each additional light source adds more light to the scene, depending on its strength, diffusion, and direction. Traditionally, light hitting a subject can be divided into three categories; key, fill, and back. The key light is the strongest light that hits the subject. This is the main light source. The fill light is any weaker light coming from a different direction than the key light. This light serves to illuminate a shadowed area on the subject cast by the key light. A back light is a special case of the fill light that comes from behind the subject to provide separation from the background. A background light can also be used, and is any light illuminating the background of an image (though key and fill lights often, for the most part, illuminate backgrounds as well). An image may be lit using only a key light (most common in naturally lit photos), or any combination of the types of light.
In balancing light, the first consideration is always the available, or ambient light. Ambient light is any light source that the photographer does not control. During the day in outdoor shots, this is usually natural light from the sun. Indoors, this may include room lights. A photographer may then choose to use other lights. A flood light is a simple lamp that is always on. Typical flood lights may include dimmers, and can be moved closer or further away from a subject as necessary. The most flexible type of photographic light, and also most useful overall, is a strobe, also known as a flash. A strobe produces a short burst of light on the order of 1/500th of a second long. Since the duration of a strobe is so short, changing the shutter speed has no real effect on changing the exposure of a strobe-lit shot. The exposure of a strobe is generally a function of strobe power, aperture, and ISO. This makes strobes a very handy lighting tool for balancing multiple lights, due to the fact that after the correct exposure for the strobe is determined using the strobe power and aperture, the amount of exposure for the ambient light can be precisely controlled by changing the shutter speed, as the shutter speed has no change in the strobe exposure. Using a slower shutter speed to include more ambient light is known as “dragging the shutter”
The balance between key and fill light is referred to as the lighting ratio. While a precise measurement of the key and fill lights could be taken and the ratios compared directly, the more common technique is to simply use a light meter to compare the proper exposure of the fill light compared to the key light. Since the key is most commonly exposed to 0, the fill will be exposed under its full exposure value. Note that one stop corresponds to a halving of light. So a 1:1 ratio corresponds to equal key and fill. A 2:1 ratio corresponds to fill one stop under key, 4:1 corresponds to fill two stops under key, and so forth. Increasing the value of the lighting ratio increases the contrast of the image.
The color balance of the light regards the particular tint of the light being used. White light is made up of a combination of all the colors in the spectrum, and most light used in photographs is “white”. However, the balance of all the colors that make up a particular white light usually give the light a particular tint, or cast. Fluorescent lights have strong green characteristics. Flash units tend to have strong blues. Tungsten lamps are often orange or reddish. The sun is generally regarded as neutral when high in the sky, but as the sun sets, it becomes increasingly warm toned.
As the color balance of the light being used changes, it is often appropriate to set the white balance, that is, return the “white” light in the image to a neutral value. This can either be set in-camera or in post-processing. This topic will be revisited when discussing image processing.
