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Digital Photography Fundamentals
If you just bought your first digital camera, or if you would like a refresher on the fundamentals of photography, this chapter is for you. If you believe you have a solid grasp of the basics (aperture, shutter speed, ISO, depth of field, exposure modes, auto-focus modes, meter modes, white balance, etc.), you may wish to skip to chapter 2.
A modern digital camera can rightly be called “a computer with a lens.” After spending all that money on the latest gee-whiz electronic gadget, you may well be thinking, “Why do I need to learn all this technical stuff about photography? Why not let the camera pick the right aperture, shutter speed, ISO, and white balance (whatever that is)? I’ll worry about the fun, creative stuff—choice of subject, composition, and timing—and let the camera handle the rest.”
Sometimes “auto-everything” will indeed give you exactly what you want. In many of the most exciting photographic situations, however, auto-everything will fail miserably. If you really want to master the art of photography, you should start by mastering the craft.
The Exposure Triangle
Correct exposure is the foundation for all successful images. Three parameters control exposure: aperture, shutter speed, and ISO. These parameters together are called the exposure triangle.
The aperture is the hole in the diaphragm, inside the lens, which allows light to reach the sensor when the shutter is open. The bigger the hole, the more light reaches the sensor for every second that the shutter is open.
The diameter of this hole is specified as a fraction of the focal length of the lens. (The “f” in the f-number stands for focal length.) An aperture of f/2 on a 50mm lens, for example, is 25 millimeters in diameter: 50 divided by two equals 25. For the purpose of calculating exposure, however, we really don’t care about the diameter of the opening; we care about its area, because it’s the area of the aperture that ultimately controls how many photons reach the sensor for each second of exposure.
The standard f-stop sequence is f/1.4, f/2, f/2.8, f/4, f/5.6, f/8, f/11, f/16, f/22, and f/32. This seemingly illogical series of numbers actually makes perfect sense: each full-step change in the f-stop represents a doubling or halving of the area of the aperture, not the diameter. As a result, each full-step change represents a doubling or halving of the amount of light reaching the sensor for every second that the shutter is open.
FIGURE 1-2 Marcellina Mountain and the Raggeds, Raggeds Wilderness, Gunnison National Forest, Colorado. Ebony SW-45 field camera, Fujichrome film. Lens and exposure unrecorded.
You should memorize the standard f-stop sequence just like you memorized your multiplication tables long ago. Changing the aperture from f/8 to f/5.6, for example, doubles the area of the aperture. Because f-numbers are fractions, large f-numbers such as f/16 or f/22 represent small holes through the lens. Small f-numbers such as f/1.4 or f/2 represent large holes through the lens. Remember it this way: one-sixteenth of a pie (f/16) is a very small sliver; one-half of a pie (f/2) is an enormous serving. (By default, on most cameras, one click of a wheel changes the aperture by one-third stop, which means three clicks are required to change the aperture by one full stop.)
The shutter speed is much easier to understand. It’s just the length of time the shutter is open. (It has nothing to do with “speed” in the sense of distance traveled in a particular amount of time.) As with the aperture, each full-step change in shutter speed represents a doubling or halving of the amount of light reaching the sensor. Changing the shutter speed from 1 second to 2 seconds, for example, doubles the amount of light reaching the sensor. Similarly, changing the shutter speed from 1/60th to 1/125th of a second halves the amount of light reaching the sensor.
FIGURE 1-3 Claret cup cactus and the Narrows, Black Canyon of the Gunnison National Park, Colorado. I used a small aperture (large f/number) to give this image deep depth of field. I enhanced the depth of field further by using a tilt-shift lens, which allowed me to tilt the plane of focus forward so it ran from the flowers in the foreground to the canyon rim in the background. Canon EOS 5D Mark III, Canon TS-E 24mm f/3.5L II tilt-shift lens, 0.6 seconds, f/16, ISO 100.
FIGURE 1-4 Columbine Falls and Mt. Meeker at sunrise, Rocky Mountain National Park, Colorado. Shutter speeds in the range of 1/4 to 1 second blur falling water in an attractive way. Too short a shutter speed freezes the water; too long turns it into featureless smoke. Zone VI 4×5 field camera, Fujichrome film. Lens and exposure unrecorded.
Think of correct exposure as the amount of water required to fill a bucket. You could use a small hose (a small aperture, such as f/16 or f/22) and open the valve controlling the water for a long time (a long shutter speed) and fill the bucket. Or you could use a large hose (a large aperture, such as f/2.8 or f/4) and open the valve for a short time (a short shutter speed) and still fill the bucket. In other words, there’s a reciprocal relationship between aperture and shutter speed: you can use a long shutter speed and a small aperture, or a short shutter speed and a large aperture, and get the same result in terms of exposure.
So if you can fill the bucket either way, why does it matter which way you use? Here’s why: the aperture controls the depth of field the image will show, while the shutter speed controls the appearance of objects moving across the frame. Using a small aperture, such as f/16 or f/22, means the image will exhibit deep depth of field. For example, the zone of apparent sharpness in the image might extend from the flowers 2 feet from the camera to the mountains 2 miles away. Most landscape photos are shot with a small aperture so that everything in the image is sharp. Using a large aperture, such as f/2.8 or f/4, creates shallow depth of field. The depth of field might extend from just 6 feet to 8 feet, for example. Shallow depth of field is often appropriate for portraits of people and wildlife so that the sharp subject stands out from the blurry background.
Short shutter speeds freeze motion in the subject, which is appropriate in many sports shots. Long shutter speeds blur motion, which may be pleasing when shooting waterfalls, for example.
Notice that there’s always a trade-off at work. If you want a faster shutter speed, you must accept less depth of field. If you want more depth of field, you must accept a slower shutter speed.
At this point a savvy reader might ask, “Why can’t I just raise the ISO and get both depth of field and a fast shutter speed?” Unfortunately, there’s no free lunch.
ISO, the final parameter in the exposure triangle, is often described as the sensitivity of the sensor, but this is a bit misleading. Increasing the ISO doesn’t change the efficiency of the sensor, meaning the percentage of incoming light that is converted to an electric signal. Increasing the ISO merely amplifies the signal coming off the sensor. Changing the ISO does not change the amount of light reaching your sensor. There are only two factors that control how much light reaches your sensor: aperture and shutter speed. If aperture and shutter speed are held constant, the amount of light reaching your sensor is also constant, regardless of the ISO you set.
All sensors generate noise—random, unwanted variations in the strength of the signal coming off each picture element on the sensor, which results in small, random variations in color and brightness in the image. A noisy digital image resembles a grainy image shot on high-speed film in the days of yore. If the light reaching the sensor (the signal) is strong, then you have a good signal-to-noise ratio and you have a clean image, with very little visible noise. As the amount of light reaching the sensor decreases, the signal coming off the sensor gets weaker in proportion to the noise. Your signal-to-noise ratio deteriorates. Increasing the ISO increases the amplification of the signal, but also amplifies the noise. You may need a high ISO to get a fast-enough shutter speed to stop action in low light, but the image will be noisier.
Digital sensors have one native ISO, which is usually the lowest ISO you can set by pushing a button and spinning a dial. It’s normally 100, but varies a bit depending on the camera. That ISO will give you the highest quality image your camera can produce. Using ISO settings like Low 1 or Low 2 will give you a slower shutter speed, which may be useful when intentionally blurring the subject, but it won’t create an image with lower noise.
ISOs are like shutter speeds in that doubling or halving the ISO number has the same effect on the density of the image as doubling or halving the shutter speed. If an image is too dark, for example, you could double the shutter speed, say from 1 second to 2 seconds, or double the ISO, say from 100 to 200, and the effect on exposure would be the same. Objects moving within the frame would exhibit more blur with the longer shutter speed, of course; the overall image may be noisier if you chose to increase the ISO instead of doubling the shutter speed.
In general, I suggest turning off auto-ISO and picking the ISO you want yourself. Most good landscape images are shot on a tripod, so shutter speed is largely irrelevant unless parts of the subject are moving (flowers blowing in the wind, for example). I do sometimes use auto-ISO when shooting wildlife in low light. I set the lens to its largest aperture so the camera gathers as much light per second of exposure as possible. I know I need a minimum shutter speed to be able to hand-hold a long lens and get a sharp image, so I set that shutter speed using manual exposure mode (more on that later). I then set the ISO to auto to automatically obtain a correct exposure even in low light. I’d rather deal with a noisy, sharp image (probably salvageable) than a clean but fuzzy image (probably a throwaway).
All this talk about meters may lead you to believe that the exposure chosen by the meter will always be right. In fact, there are a number of situations where you will either want to override the meter’s recommendation, or where you will want to shoot two or more different exposures of exactly the same composition, then combine those frames later in a variety of ways. I’ll have a lot more to say about exposure in chapter 7, and in particular about the essential exposure tool called the histogram, but for now I just want you to think of the meter reading as a starting point, and not as an ironclad guarantee of perfect exposure.
FIGURE 1-5 Aurora over the Brooks Range, near Wiseman, Alaska. The aurora moves constantly. Shooting with a high ISO is necessary to keep the shutter speed short enough to preserve the aurora’s interesting structure. When shooting the aurora, “short” is a relative term; I exposed this image at 13 seconds, f/2.8, ISO 3200. Canon EOS 5D Mark III, Canon EF 16-35mm f/2.8L II USM at 16mm.
FIGURE 1-6 Mt. Monolith and sastrugi, Tombstone Territorial Park, Yukon Territory, Canada. Brilliantly lit snow scenes like this one are a classic example of a situation where you will want to override your meter’s exposure recommendation. The ideal exposure for a snow scene renders the brightest snow as near-white, but with printable detail. Large areas of completely blank white are generally unacceptable in a landscape image. Canon EOS 5D Mark III, Canon EF 16-35mm f/2.8L II USM at 27mm, focus-stacked, 1/200th, f/16, ISO 100.
Depth of Field and Hyperfocal Distance
In a sense, depth of field is an optical illusion. You can only focus a lens at one distance at one time. Only objects at that distance will be as sharp as the optical system can deliver. Objects closer than the focused distance, as well as those farther away, will become increasingly blurred as the gap between them and the focused distance becomes larger and larger.
Fortunately for photographers, our eyes are imperfect. They do not have infinite resolving power. If the blurry edge of an object is narrow enough, we still see that object as sharp. One widely accepted standard for “sharp” is that the blurry edge cannot be more than 1/100th of an inch wide in the print. Since all prints require enlarging the tiny image captured by the sensor, the blurry edge on the sensor must be narrower still. In optical parlance, sharpness on the sensor is defined as the size of the circle of confusion—the diameter of a circular spot on the sensor representing the out-of-focus image of a single, infinitely small point on the subject. In practical terms, think of the circle of confusion, often abbreviated CoC, as the width of the blurry edge of an object. Many depth-of-field tables use a CoC of .03mm, which translates to a blur zone of 1/100 of an inch in an 8×10 inch print. I prefer a tighter standard of sharpness of 0.02mm, which translates to a blur zone of 1/150 of an inch in an 8×10-inch print.
FIGURE 1-7 Yellow fawn lilies (also known as glacier lilies or avalanche lilies) in Fox Park, Indian Peaks Wilderness, Colorado. This image exhibits the deep depth of field typically considered desirable in a landscape image. Zone VI 4×5 field camera, Fujichrome film. Lens and exposure unrecorded.
With that as background, you can now understand that depth-of-field tables are based on a series of assumptions, in particular how big a print you want to make, how closely you want to view it, and how tight a standard for sharpness you want to use. Let’s say an image has a depth of field from 2 feet to infinity when printed at 8×10 inches and viewed from a foot away. That same image may have a depth of field from 4 feet to infinity if you make a 30×40-inch print and view it from a foot away. View that 30×40-inch print from 5 feet away, however, and once again it has a depth of field from 2 feet to infinity. Our ability to resolve fine detail steadily declines as we get farther and farther from the subject. For example, you can easily read a book held at arm’s length. Place it 20 feet away, and the task is impossible. As a practical matter, most people tend to view prints from a distance roughly equal to the diagonal dimension of the print, or about a foot away for an 8×10-inch print. Of course, for a photographer, the viewing distance is limited only by the length of the photographer’s nose.
To achieve the maximum depth of field possible for a given focal length and aperture, you should focus the lens at the hyperfocal distance. Depth of field then extends from one-half of the hyperfocal distance to infinity. For example, the hyperfocal distance for a 24mm lens on a full-frame camera at f/22 is 4 feet 3 inches (CoC .02mm). If I focus the lens at that distance, depth of field will extend from 2 feet 1 inch to infinity.
There are many good smartphone apps for both iOS and Android that contain depth-of-field and hyperfocal-distance calculators for your sensor size, focal length of lens, and aperture. Some even let you choose the size of the circle of confusion you want to use.
You should think of depth-of-field and hyperfocal-distance calculators as optimistic. They provide a minimal level of sharpness that will be acceptable in magazine-size prints but may not deliver the sharpness you want in a big print. If your composition requires that you obtain the maximum depth of field possible, then by all means use them. If, on the other hand, you’re shooting with a wide-angle lens and the closest object is 50 feet away, don’t focus at the hyperfocal distance. Instead, focus on the closest object (which, optically speaking, will essentially be at infinity with a wide-angle lens), stop down to f/8 or f/11 (usually your sharpest apertures), and fire away.
FIGURE 1-8 The Flatirons and sumac in fall color at sunrise after the first snow, Chautauqua Park, Boulder Mountain Parks, near Boulder, Colorado. To obtain maximum depth of field with my 50mm lens, I set the aperture to f/32 and focused at the hyperfocal distance of 13 feet (CoC .02mm), which gave me depth of field from 6 ½ feet to infinity. Canon EOS 1Ds Mark III, Canon Compact-Macro EF 50mm f/2.5, 1/6th, f/32, ISO 100.
All of these calculations can seem rather befuddling when you’re hypoxic and sleep deprived. To double-check that you’ve got it right, shoot a test frame, enlarge it on your LCD by a factor of 10, and scroll back and forth across the image to be sure everything is sharp. The LCD on older cameras may look fuzzy everywhere at 10×, limiting the usefulness of this approach, but newer cameras will give you a clear view. Many Nikons allow magnification beyond 10×, which on some LCDs makes everything look blurry. You may need to zoom back out a step or two to assess sharpness accurately. When in doubt, compare sharpness at the focused distance (which should be razor-sharp if you’re on a good tripod) with sharpness at the near and far limits of your composition.
Exposure Modes
Exposure modes are the different ways your camera offers to achieve correct exposure, from fully automatic to fully manual. In auto-everything mode, often marked with a green A or the equivalent on the exposure-mode dial or in a menu, the camera picks all three of the parameters that control exposure: aperture, shutter speed, and ISO. It will assume you’re hand-holding the camera and choose those three parameters to give you a shutter speed fast enough that you can hand-hold the camera and still get sharp images. But as we’ve seen, there are many situations where you want to take control of those parameters yourself to achieve the image you imagine. For example, if you’re shooting a landscape from a tripod and nothing is moving within the frame, you’ll want a large f/number (small aperture) for deep depth of field and a low ISO for highest image quality. You don’t care if the shutter speed is too slow to hand-hold because you’re not hand-holding. If you’re shooting a fast-moving sport like alpine skiing, your top priority may be a fast shutter speed, and you’re willing to sacrifice depth of field by using a small f/number (large aperture) and perhaps even going to a higher ISO to achieve that action-stopping shutter speed.
FIGURE 1-9 Sunshine Peak at sunrise from the summit of 14,034-foot Red-cloud Peak, Redcloud Peak Wilderness Study Area, near Lake City, Colorado. For evenly lit, midtone subjects such as this one, aperture priority is usually the best choice. Since depth of field was not an issue, I set the aperture to f/8, the sharpest aperture on my Canon 70-200mm f/4 lens. Choosing aperture priority rather than manual exposure meant the camera adjusted the exposure automatically as the intensity of the light changed rapidly at sunrise. That freed me to concentrate on composition and timing rather than exposure. Canon EOS 5D Mark III, Canon EF 70-200mm f/4L IS USM at 93mm, 1/20th, f/8, ISO 100.
In program mode, most cameras will choose an aperture and shutter speed combination that will deliver correct exposure and that the camera thinks is hand-holdable. The camera will respect the ISO setting you’ve chosen unless you’ve set the ISO to auto, in which case the ISO will vary, again in an attempt to create a hand-holdable shutter speed and a good compromise between depth of field (large f-number) and low ISO. Some cameras also offer a Program-Shift mode, which allows you to change the aperture and shutter speed in tandem while still maintaining correct exposure. Although program mode has its place, using it means relinquishing control over important aspects of your image’s appearance.
You can create the look you want and still let the camera make the final exposure decision by using either aperture-priority or shutter-priority auto-exposure. In aperture-priority auto-exposure, you pick the aperture, and the camera picks the shutter speed to achieve correct exposure. This mode is appropriate for landscapes, where depth of field is often the overriding consideration. In shutter-priority auto-exposure, you pick the shutter speed, and the camera picks the aperture to achieve correct exposure. This mode works well for action subjects, where the overriding concern may be stopping the action. The danger with shutter priority is that your lens may not offer a wide-enough aperture to allow you to use the shutter speed you want, particularly in low light. For example, let’s say the shutter speed you need to stop a skier flying down the hill is 1/500th of a second. You set the ISO to 100 to get the best quality. Unfortunately, to achieve correct exposure in failing light you need an aperture of f/1.4. If the widest aperture your telephoto allows is f/2.8, your shot will be two stops underexposed. (There’s a two-stop difference between f/1.4 and f/2.8.) You can’t lengthen the shutter speed and still stop the action. You can’t open the lens any farther because you’re already shooting wide open. The best solution in this case is to raise the ISO by two stops, to ISO 400, to achieve correct exposure.
FIGURE 1-10 Columbine and Parry’s clover in Vestal Basin, Weminuche Wilderness, Colorado. Close-ups of wildflowers are another example of a situation where aperture priority is usually the best choice. Most wildflower close-ups look best under cloudy skies. Inevitably, the correct exposure will vary constantly as the sun dances in and out of the clouds. By choosing aperture priority, you can fire the moment the wind stops and the light is soft. If you were shooting in manual exposure, the perfect moment would be likely to pass as you adjusted the shutter speed to obtain correct exposure. Canon EOS 5D Mark III, Canon EF 16-35mm f/2.8L II USM at 35mm, 1/100th, f/16, ISO 400.
In manual mode, you set the aperture and shutter speed, and, if desired, the ISO as well, and the camera does whatever you tell it to, regardless of whether the result will be a correct exposure or not. Manual mode is best reserved for situations where you know you need to override the camera meter’s recommendation or where you need to lock in the exposure regardless of what the meter is telling you. As I’ll discuss in detail in chapter 7, meters assume that the world, on average, is a middle tone, or, in black-and-white terms, a middle gray. If you’re photographing a subject that isn’t a middle tone, such as a white waterfall or a bison’s black-furred, shaggy head, you’ll need to compensate. Manual exposure can be a good way to ensure the camera does what you want. Panoramas are a situation where manual exposure is essential. You don’t want the exposure changing as you pan across the scene from one camera position to the next. If, however, you’re simply accepting the camera meter’s recommendation and setting the aperture and shutter speed to match, you’re making more work for yourself than necessary. When I’m shooting landscapes, I typically use aperture priority unless I can articulate a clear reason why I should switch to manual exposure.
Auto-focus Modes
Auto-focus is a great boon for photographers, but it contains a pitfall you must avoid. Nearly all cameras come from the factory set up so that pressing the shutter release halfway down turns on the meter and starts auto-focus. The camera may use a single auto-focus point or multiple points to focus on that part of the scene that lies under the point or points. In many situations, that works well, but it can trip you up if you’re trying to achieve maximum depth of field. Let’s say you’re using a single, centrally located auto-focus point and shooting the scene with a 24mm lens at f/22. The hyperfocal distance for that lens at that aperture is 4 feet 3 inches, so you focus on a rock that you estimate is 4 feet 3 inches away and expect depth of field from 2 feet 1 inch to infinity. To focus on the rock, you had to place it in the middle of your viewfinder, but that’s not where you want the rock to be in the final composition, so you recompose to place the rock near the bottom of the frame. Oops! Now when press the shutter release all the way down to take the picture, the camera will refocus on whatever happens to be under the central auto-focus point, which may be much farther away than 4 feet 3 inches. You’ve lost your depth of field.
One solution to this problem is to move the auto-focus point so it is positioned on top of the rock when your composition is correct. Another is to turn off auto-focus and focus manually on the appropriate rock. A third is to use auto-focus to focus on the rock, then turn off auto-focus. The best solution is to take a deep dive into your menus, remove the auto-focus function from the shutter release, and assign that function to a button on the back of the camera. Now pressing the shutter release halfway down will only activate the meter. When the time comes to auto-focus, you press the auto-focus-on (AF-on) button with your thumb, then remove your thumb from the button, recompose, and take the shot.
FIGURE 1-11 The Sangre de Cristo Range at sunset from the summit of Star Dune, Great Sand Dunes National Park, Colorado. If I had composed the shot, then used the central auto-focus point to focus, I would have focused beyond the hyperfocal distance and not achieved full depth of field. Canon EOS 5D Mark IV, Canon EF 16-35mm f/2.8L III USM at 28mm, 1/6th, f/16, ISO 100.
FIGURE 1-12 Continuous auto-focus is the best mode for fast-moving action like this mountain goat leaping over a stream, Chicago Basin, Weminuche Wilderness, Colorado. Canon EOS 5D Mark III, Canon EF 70-200mm f/4L IS USM at 70mm, 1/4000th, f/4, ISO 400.
Auto-focus has grown increasingly sophisticated over the years, but it still comes in two main types: continuous auto-focus and focus-priority, often called single-shot auto-focus. With continuous auto-focus, as the name implies, the camera tries to maintain continuous sharp focus on whatever is under the active focus points. You can fire the shutter at will, whether or not the camera thinks the lens is in focus. This is the mode to use if you’re shooting birds in flight or elk running across a meadow. With focus-priority, the shutter will not fire unless the camera thinks the lens is in focus. This is a good mode for portraits, where the subject is stationary. If you’re shooting landscapes using rear-button focus, it doesn’t matter much which mode you choose. Focus the lens at the distance required to get the depth of field you want, remove your thumb from the AF-on button, and shoot.
Meter Modes
Most cameras offer a variety of meter modes, which refer to the different ways that the meter can measure light reflected from the scene. Those modes typically include multi-segment, in which the camera attempts to intelligently analyze the intensity of light coming from all parts of the scene. For example, in theory, the camera should be able to exclude a small but very bright light source, such as the sun, from its exposure calculation. Canon calls this mode Evaluative; Nikon calls it Matrix; other manufacturers use other terms. Other common metering modes include center-weighted averaging, where the meter looks at light from all parts of the scene but gives extra weight to the light coming from the center of the scene, and spot-metering, in which the meter reads only the light coming from a small area in the center of the frame, excluding other areas of the frame from its calculation. Although all these modes have their place, your best bet is to stick with multi-segment for virtually all of your shooting, particularly when you’re just starting out.
RAW Versus JPEG
Most modern cameras can record images in two different file formats: RAW and JPEG. The differences are technical, but the bottom line is this: RAW files give you much more editing flexibility. You can pull much more highlight and shadow detail out of a RAW capture of a high-contrast scene than you can a JPEG capture, as you can see in figures 1-13 and 1-14. The only real disadvantage of RAW files is that you must have editing software, such as Lightroom or Adobe Camera Raw, which ships with Photoshop, that will handle them. If you’re serious about photography, however, acquiring suitable editing software and learning to use it is essential to producing top-quality photographs. For the remainder of this book, my instructions will assume you are shooting RAW images.
FIGURE 1-13 I set my camera temporarily to shoot RAW+JPEG and exposed both images at the meter’s recommendation. (Normally I only shoot RAW files.) The RAW file is on top; the JPEG file is on the bottom. The meter read off the dark trees, giving them adequate exposure but rendering the sky very bright. I then opened both images in the Develop Module in Lightroom Classic. In the Basic panel, for each image, I set Highlights to -100, set Shadows to +30, set Contrast to +35 points of contrast, and applied a Graduated Filter with a -0.5 exposure change to the sky. I was able to recover good color and detail in the sky in the RAW file; the sky in the JPEG, on the other hand, shows poor color and severe banding. Canon EOS 5D Mark III, Canon EF 16-35mm f/2.8L III USM at 35mm, 0.6 seconds, f/16, ISO 100.
FIGURE 1-14 I set my camera temporarily to shoot RAW+JPEG and exposed both images at two stops darker than the meter’s recommendation. (Normally I only shoot RAW files.) The RAW file is on top; the JPEG file is on the bottom. I then opened both images in the Develop Module in Lightroom Classic. In the Basic panel, for each image, I set the Exposure slider to +2 and Shadows to +30. I was able to recover good detail in the shadowed trees in the RAW file, but the shadowed trees in the JPEG remained almost black. Canon EOS 5D Mark III, Canon EF 16-35mm f/2.8L III USM at 35mm, 1/6th, f/16, ISO 100.
White Balance
Human vision has a property called color constancy that makes objects appear to have the same color regardless of the color of the light they are in. For example, we see a bride’s white wedding dress as white regardless of whether she’s standing in noon sunlight, in the shade of a building on a clear day, under tungsten light at the altar, or under fluorescent light at the reception. Without intervention, a camera’s sensor would see those four scenes very differently. It would record a white wedding dress and natural skin tones when the bride was standing in the parking lot, but it would record a cold, blue bride when she’s standing in the shade on a clear day, when the light illuminating her comes from the blue sky. It would record a badly sunburned bride when she’s standing under orange tungsten light at the altar and record a rather seasick green bride when she’s standing under cheap fluorescent lights at the reception. To overcome this problem, camera manufacturers invented auto white balance, which is a great tool for wedding photographers. Auto white balance attempts to mimic the color constancy property of our visual system. In other words, auto white balance attempts to keep white wedding dresses white, which in turn means that the bride’s flesh tones will look natural. Put another way, auto white balance attempts to remove any color casts the color of the light may introduce.
As useful as auto white balance can be, it is not a good tool for landscape photographers. If we are so fortunate as to see wonderful golden light suffusing our scene at sunrise or sunset, we want to preserve those warm hues because they are part of what makes the image beautiful (figure 1-15). If you choose auto white balance, the camera will think, “Oh! You’re shooting under tungsten light and want me to cool down the image!” When shooting landscapes, I always shoot with a daylight white balance. Choosing a daylight white balance essentially tells the camera, “Record the wavelengths actually present in the scene. Don’t ditz with the color.”
It’s quite true that you can use editing software to change the white balance of an image after the fact if you’re shooting RAW files. For JPEG files, the white balance is baked into the file and can only be changed with difficulty and within narrow limits. This limitation of JPEG files is another compelling reason to shoot RAW.
Mastering the fundamentals of digital photography is like playing scales on the piano. It may seem tedious, but it will give you an essential grounding in the craft. Master the craft, and your images will soon begin to blossom into art.
FIGURE 1-15 The image on the left shows how the camera would have recorded the scene with the white balance set to auto. The image on the right was shot with the white balance set to daylight. Canon EOS 5D Mark III, Canon EF 16-35mm f/2.8L II USM at 29mm, 1/5th, f/16, ISO 100.