The interrelationship between film and light is at the heart of the photographic process. Everything else is merely an accessory to these two fundamental elements. How the two react to each other is the most important thing you must learn to become a good photographer.

Many people assume that film is film, and that the camera knows what the exposure should be. They're content to let the photo fall where it may. But for the serious nature photographer, this isn't an option. Most of the joy of outdoor photography is in the details of light and color. The way you control these elements is by learning what films will bring out colors and what types of lighting will achieve the mood you're trying for. Understanding these elements is the foundation for all your future photographic success. Once you have a grasp of these fundamentals, the sky is the limit. You'll have the essential tools for making your individual statement about how you see the world, and you'll find dozens of ways to manipulate every scene.

PAINTING WITH LIGHT

Light is the medium that you've chosen to record your creative ideas. A painter uses oil, acrylic, or watercolor as the medium. For you, the photographer, light is your paint. Fancy equipment, film, accessories, beautiful subjects-all are of absolutely no value unless you know how to control the light that comes into your camera.

Today's cameras are capable of doing most of the work of finding the correct exposure setting for a given scene. Modern equipment has become extremely sophisticated in the way it measures incoming light. But it would be a mistake to think that you don't need to know anything about exposure and metering systems. Although the camera uses a very specific set of rules that work much of the time, they are by no means perfect.

The camera's exposure meter is designed to give proper exposure for subjects of middle tone, the gray tone halfway between light and dark. The exposure meter chooses the correct exposure for recording your subject in the midrange between light and dark.

If the scene contains high contrast, many meters will try to average the light. This will leave the lighter areas burned out (overexposed) and the dark areas black (underexposed), a sure way to get an unsatisfactory photograph.

Some cameras have a spot-metering system that lets you choose the area of the frame you wish to have exposed properly. This makes things a little easier, but you alone should make the final decision on your exposure setting. Photography is a creative endeavor, and the way you control the light that strikes your film is the single most important factor dictating how your final product will look.

Certain lighting conditions can confuse the camera system; what you want well lit may not be what the camera is concentrating on, for instance. So even if you have a camera with automatic exposure (AE) settings, read your manual thoroughly so you understand how to override these automatic settings. Once you know how your camera works, adjusting your meter setting to suit your needs is usually a simple matter. Flaving a fundamental understanding of the way light works and how your camera measures light is the key to successful photographs. We'll address your meter options in more detail in chapter 2.

MEASURING AND CONTROLLING LIGHT

The light that comes into the camera is controlled by two settings-shutter speed and aperture. Each is represented in increments called stops. Each stop either doubles or halves, depending on which direction you are adjusting, the amount of light that reaches the film. Controlling the light that reaches the film is a matter of combining these two settings to create the effect you wish to achieve. Each control method provides different attributes, so understanding them independently will maximize your control over your images.

This bears repeating: shutter speed and aperture always work together.

SHUTTER SPEED

Shutter speed measures how long the shutter will be open to let light reach the film plane. Most camera shutter speeds begin on the low, slow end with "B," a symbol that stands for "bulb," the squeeze-ball shutter release that was the only option on early cameras. When your shutter-speed dial is set on "B," the shutter will stay open for as long as you hold down the shutter release. The upper, fast end of the shutter-speed scale is anywhere from 1/1000 to 1/4000 a second. Shutter speeds are referred to by only the denominator of the fraction-a speed of 1/125, for instance, is called 125, and this is how the speed appears on instruments. Therefore, the higher the number, the faster the shutter speed, or the smaller the increment of time that the shutter remains open.

Shutter speed is used to control how the motion of your subject is recorded-the less time the shutter is open, the more that the motion is frozen. For example, if you shoot a running deer at 1/60, he will probably come out blurred, because you've captured his motion over the course of 1/60 second. This may not seem like a long time, but for a quickly moving object it is. But if you shoot the deer at 1/250, you'll probably succeed in fully stopping his motion.

Conversely, you can shoot an absolutely stationary object at as slow a shutter speed as you wish, if you can control all motion of your camera or subject. (These objects are very rare in nature photography-there is virtually always some sort of breeze!)

The most common shutter speeds that you will find and use on various cameras are I second, 1/2, 1/4, 1/8, 1/15, 1/30, 1/60, 1/125, 1/250, 1/500, 1/1000, 1/2000, and 1/4000.

To understand how the camera shutter works, open up the back of your camera (without film in it!). Take the lens off the camera or open the aperture on the lens to its widest opening, which will be a measurement such as f1.4 or f2.

Set your shutter-speed dial at "B" and press the shutter-release button, just as though you were taking a regular picture. The shutter will stay open as long as you hold down the button. Now set it at I second and release the shutter-notice that a full second seems like a long time. For photographic purposes, it is. Now work your way through the entire set of shutter speeds on the dial and watch how quickly the shutter opens and closes. This will give you a good sense of how much light reaches the film for each different shutter speed.

As you work from 1 second through the faster shutter speeds, the time is reduced by half at each subsequent shutter speed: 1/2 second is half the time, and half the light, of 1 second, but 1/125 is also half the time, and half the light, of 1/60 second. The faster the shutter speed, the less light is allowed onto the film.

Now let's reverse the procedure. A shutter speed of 1/125 is half as fast, or twice as much light, as 1/250, 1/30 is half as fast, and twice the light, as 1/60. The slower the shutter speed, the more light is allowed to be exposed to the film.

So shutter speed controls the amount of motion recorded in your photographs. You'll require shutter speeds of 1/125 and higher to stop motion. For example, 1/125 may stop the movement of a swimmer, but catching bicycle racers might require 1/500. Slower shutter speeds (1/60 and lower), on the other hand, will create a blurred image if your subject is moving.

Of course, shutter speed isn't the full story; now we're ready to add aperture setting to the exposure equation. These two controls always work together.

Aperture

Aperture is the measurement that indicates the size of the lens opening. This, along with the amount of time that the lens is opened, determines how much light will reach the film. Aperture settings are known as f-stops, and are designated by the letter "f followed by the size of the opening; these settings are found on the lens itself. Each lens has a different range of aperture settings based on its speed. (Lens speed is determined by the largest aperture setting for the lens. Faster lenses have wider aperture openings, such as fl.2 to fl.8. The largest aperture opening on slower lenses is f2.8 to f5.6.)

Standard aperture settings range from fl.4 to f32, but each lens may have a different range of aperture numbers. The smaller the number, the larger the lens opening. An fl.4 aperture creates a large opening; an f32 creates a very small opening.

The most common aperture settings you'll find on a lens are fl.4, f2, f2.8, f4, f5.6, f8, f11, fl6, f22, and f32. Each number in the series, working from the largest opening of fl.4, will transmit half as much light to the film as the previous number. For example, f2 transmits half as much light as fl.4, and fl I allows half as much light as f8 to reach the film.

In reverse, f8 transmits twice as much light to the film as f11, and fl.4 allows twice as much light to expose the film as f2.

Play with your lens to see what we mean. As with shutter speed, an easy way to understand aperture is to take your lens off the camera. Look through the rear of the lens and turn the aperture settings from largest to smallest. Turning the aperture to the largest number, probably f22 or f32, will create a pinhole opening. Turning it to the smallest number, fl.4 or f2, will create an opening almost as large as the entire width of the lens. Every f-stop represents a halving or doubling of the light you will let into the camera through this opening. Nearly all 35mm SLR cameras will also allow you to adjust apertures by1/2-stop increments. These are the spaces between the "clicks," which allow you to fine-tune the amount of light for a given exposure. Some cameras also have a separate exposure-compensation button that modifies the exposures in 1/3-stop increments.

Aperture controls depth of field, the amount of the image frame that will be in sharp focus. A very small aperture opening will create an image that has most of the frame in focus. In contrast, a large aperture will have only the central subject in focus-the background and foreground will be thrown out of focus.

The key to getting the exposure you want is finding the appropriate combination of aperture and shutter speed. Though any situation may be shot with a variety of correct combinations, not every combination will look the same. A high shutter speed with a large aperture will capture the motion of a central subject in good detail. A slow shutter speed with a small aperture will give you excellent depth of field, and everything in the frame will be in sharp focus, although any movement will be blurred. Try shooting different exposure combinations of a subject and see for yourself the differences in sharpness or depth of field.

LIGHT CONDITIONS

There are a number of conditions that cause special concerns for the nature photographer.

Bright Sunlight

You'd think that a bright, bright sunlight creates its

sunny day would be a perfect time to shoot pictures outdoors. But own special issues. Because of the way light is reflected, your meter's exposure reading can be thrown off by bright surfaces such as water or sky, as well as by dark surfaces such as a deep green forest. That's why it's handy to learn the Sunny 16 Rule, a quick way to estimate the correct exposure setting for bright conditions. Its also a handy backup system if you suspect your meter is malfunctioning.

Sunny 16 Rule
Shutter Speed = 1/ISO speed at f16

Using this equation, your aperture is always set at fl6. If you're shooting with ISO 125 film, your shutter speed should be set at 1/125 second. You can round off to the nearest number, as long as it is within 1/3 stop-if you're using ISO 100 film, then, you should get a good exposure using a shutter speed of 1/125 second.

With the Sunny 16 Rule, always bracket to ensure that you capture the exposure you want. Bracketing means shooting at 1/2 to I stop under the recommended exposure, then shooting again at 1/2 to I over the recommended exposure. Of course, you'll also take one shot at the exposure you believe is correct.

The Sunny 16 Rule can be the basis for determining your exposure in a number of conditions. If your shot is made up primarily of water or snow, stop down 1 to 1 1/2 stops from this setting. If conditions are hazy with no shadows, open up 1 stop.

High-Contrast Subjects

On some occasions you'll run into a scene that has virtually every value of light in the spectrum. Unfortunately, your camera will be able to pick up only some of the subtleties that your eye can see. Your job is to choose which values are most important to you and find the balance that will achieve your purpose.

If the primary area of interest is in the darker portion of the frame, open up your exposure setting I or 2 stops above what the camera suggests. Remember that the brighter portion of the shot may blow out-that is, all detail will be completely erased.

On the other hand, if this brighter portion is what you hope to capture, simply stop down I or 2 stops from the camera's suggested setting. This will send the darker portion of the frame nearly to black.

Is it possible to have it all? Often it is, if you're willing to bring a few accessories along. Reflectors can bounce a little extra light into the shadowed area. Or you can diffuse or even

block sunlight from hitting the brighter spots in the shot. Of course, this only applies to scenes small enough to control. Shots of people and close-ups can easily be controlled with a few accessories. We'll tell you more about these accessories in future chapters.

Back Lighting

Backlit subjects can be some of the most frustrating, but also some of the most potentially rewarding. Light that comes from behind your main subject accentuates its shape, and this can create powerful silhouettes. A silhouette is created by exposing for the lighting behind the subject.

If you prefer to see your main subject in detail, you'll need to take your meter reading directly off the subject. If you can approach the subject, use your camera's meter to determine its proper exposure. Then step back and shoot using this setting. Try to crop or remove extremely bright or distracting areas of contrast, such as a slice of sky.

If you can't approach the subject, try estimating the exposure. Using the Sunny 16 Rule, you know the proper exposure for the image. Just open up 1 or 2 stops to get the detail in the main subject.

You may also be able to get an idea of the proper exposure by using a gray card, a piece of cardboard that is an 18 percent reflectance middle-tone gray color. Such a card will allow you to find the proper midtone reading for your light. You can then stop up or down to adjust for the subject's color.

Sometimes back lighting casts a beautiful aura around your subject. To capture this rim lighting, you'll need to find an exposure somewhere between the bright light and the dark tones of the subject. Try to meter right to the subject, then open up 1 stop.

As always when experimenting like this, bracket your images! It's easier and ultimately less expensive to bracket your photos in the camera than to try to compensate during the development process.

Low Light

The edges of light are the times of day when many outdoor photographers most actively search for the magic light. Early morning and late in the day can be special moments when light sets everything aglow. These are the times when you can capture the mood and emotion of the landscape at its finest.

Often, however, the aperture setting you need to let in the right amount of light won't match the depth of field you're trying to achieve. Or the slow shutter speed can't capture the motion you're after. To complicate matters further, the lighting at dawn and dusk is ever changing, shifting moment by moment.

To capture these many moods requires quick thinking or a lot of bracketing or both. Check your meter reading often. As the sun goes up or down, the light changes every minute.

If you're shooting the sunrise or sunset, make certain that the sun is not in your viewfinder when you take your meter reading. Take your reading off the sky to either side of the sun, or on grass or foliage nearby that's a middle tone compared to the surrounding colors.