Photography Terms: What You Need to Know

Exposure simply refers to the amount of light recorded on the film or sensor. You want the right amount of exposure to capture the image you see (or are trying to create). If you shoot a daylight scene with too much light hitting an overly high ISO sensor for too long, you'll end up with an overly bright, glaring, unrealistic image. On the other hand, a small aperture at low ISO and short shutter speed could make a daylight scene look dark and murky.

Balancing shutter speed, ISO and aperture to get the correct exposure is the key to great photography. Master this juggling act and you'll be well on your way to consistently taking great photos. (And if you have no idea what any of this means, we'll explain each of these terms later in this article.)

Luckily, there's an easy way to cheat on your exposure juggling routine. It's called bracketing. To bracket a photo manually, set your shutter speed, aperture and ISO to where you think the proper exposure is, then take the photo. Then, adjust your aperture or shutter speed to reduce the exposure slightly and take that photo. Then adjust the exposure so it's slightly more than the first photo and take that one. This series of three photos "brackets" what is, hopefully, the proper exposure. Try to hit the sweet spot between the three to capture the perfect image.

Most digital cameras make this even easier with an auto exposure bracketing mode. When this is turned on via the camera lens' settings, the camera will automatically take three photos, with properly adjusted exposure settings, every time you press the button. If you choose to handle things manually, however, it's called exposure compensation.

Aperture and f-stop are closely related terms. Aperture refers to the opening in the lens that light shines through when a photo is taken. A larger aperture obviously lets more light through. F-stop is simply the nomenclature that photographers use when discussing different sizes of aperture.

F-stops are usually given as "f/8" or "f/22." The numbers can range from less than one (only a few lenses and cameras are capable of f/0.95, for instance) to f/128. A higher f-stop indicates a smaller aperture and less light getting through. Usually, f-stops are indicated on a standard scale in which each increase represents an aperture that allows half as much light to get through. For example, f/8 allows half as much light through as f/5.6. While many cameras allow for f-stops that lie in between these standard f-stop settings, the standard scale looks like this:

f/1, f/1.4, f/2, f/2.8, f/4, f/5.6, f/8, f/11, f/16, f/22, f/32, f/45, f/64, f/90, f/128

Aperture and shutter speed are extremely important because photography is all about the manipulation of light. The proper f-stop for the lighting conditions is a major factor in the quality of the final photograph. It's hard to give specific rules for f-stop settings, because the right setting depends on a bunch of other factors, like the lens you're using, the shutter speed at which you're shooting, and the subject you're photographing. It will take some experimentation and experience with your particular camera settings to find the aperture priority that works best for you.

F-stops also allow photographers to manipulate depth of field to create different artistic effects in their photos. We'll discuss depth of field in detail later, but for now, note that a larger aperture (which has a smaller f-stop number) will give you a narrow depth of field, while smaller apertures (with larger f-stop numbers) will result in a large depth of field.

Flash can be an important light source when shooting in low-light areas or unevenly lit situations. However, even if you only shoot photos at family gatherings with an inexpensive point-and-shoot camera, you've probably already come to realize the limitations of the flash as a primary light source. Countless photos with the foreground subjects "blown out" by excessive flash and overexposure litter hard drives everywhere, leading many photographers to try and work with as much ambient light as possible. All that said, your camera's flash doesn't have to be your enemy.

If you're stuck with your camera's built-in flash and no good way to increase lighting, there are a couple of tricks for preventing flash-induced "blow out." First, back away from the subject, zooming in slightly if necessary. Try taping some white tissue paper over the flash to diffuse and soften it. Many digital cameras allow you to reduce the flash intensity through the settings menu, so try that, too. If all else fails, just stick your finger over the flash. This is a hit-or-miss method, and the photo will be dark, but if you experiment, you might capture the ambiance you're looking for.

Of course, professional photographers can play a variety of tricks with flash, from using remote flash, bouncing the flash off a reflective surface, or using a flash in the middle of a long exposure to freeze the action. You can find creative ways to get ambient light or soft light with flash. It's a very versatile lighting tool.

You've probably seen beautiful photos of flowers which are close to the camera and in crisp focus, while the background is soft and fuzzy. That is the result of a camera's limited depth of field. Depth of field can range from extremely narrow (for example, a photo of a flower in which only one petal is in focus while the rest is out of focus) to effectively infinite (such as landscape photos where everything in the image is in crisp focus).

Depth of field is primarily affected by the camera's aperture setting. As we explained above, a larger aperture (which has a smaller f-stop number) will give you a narrow depth of field, while smaller apertures (with larger f-stop numbers) will result in a large depth of field. Depth of field is also strongly affected by focal distance, which reflects both the kind of lens you're using and how close the subject is to the camera. Closer subjects will have narrower depth of field, while distant subjects can have nearly infinite depth of field.

Calculating depth of field is actually a complicated business involving something called the Circle of Confusion. If you're not interested in the math, just experiment with your camera and a variety of f-stop settings and subjects to see how you can manipulate depth of field.

Focus is a function of the camera lens and the current aperture priority. An object that is in focus in crisp and clear, while one that is out of focus will appear blurry. Photographers have many ways to manipulate and adjust focus. Some prefer to manually focus a shot using the focus ring.

Point-and-shoot camera users often rely on autofocus, which is a system that lets the digital sensor detect the subject's distance as a motor automatically adjusts the focus. Autofocus is very handy, but has its limits if you're shooting several subjects at various distances from the camera, or a moving subject toward or away from the camera.

Some modern cameras have continuous autofocus — it can actually track moving subjects and keep them in focus no matter where they go. If one of these cameras isn't in your budget, you can manually set your focus for a certain distance and time your photos when the subject reaches the right place. You can even "game" the autofocus by forcing it to focus on some object at the proper distance, then taking the actual photo of an entirely different subject that moves into that same distance.

The ISO number is a measure of light sensitivity. It originally referred to the sensitivity of a given type of film, and the standards for measuring were determined by the International Standards Organization (ISO), which is where the name comes from. In a film camera, you had to change film to change ISO. However, a digital camera allows you to change ISO through the camera's menu functions, adjusting the sensitivity of the camera sensor to an ISO equivalent number.

So how does ISO work? While your camera's built-in light meter measures light sensitivity, photographers refer to ISO as the "speed" of the film or sensor. At high sensitivity, more light is sensed within a given period of time than at low sensitivity, so high sensitivity is considered faster. Unlike aperture, ISO settings are relatively straightforward. Low ISO numbers indicate the least amount of light sensitivity, while high ISO numbers are faster, more sensitive settings.

Why not always use the highest ISO possible all the time? In film cameras, high ISO film was grainy. We didn't escape that limitation with digital cameras, but instead of grain, high ISO numbers introduce digital noise. One of the most important things a photographer can learn is how to get the best quality shot in a given lighting condition with the lowest possible ISO setting. Of course, sporting events and other fast moving action requires high, fast ISO numbers. Fortunately, those situations are usually brightly lit.

The lens is probably the most important part of the camera. Digital photography is all about capturing light, and all the light passes through the lens. On less expensive cameras, the lens is built into the camera's body. A single lens reflex camera (known as SLRs) has interchangeable lenses. The camera body has a metal ring where the lens attaches. The attachment point also has electronic connection points so the camera can control the focus and zoom motors on the lens. There are also digital single lens reflex cameras, otherwise known as a DSLR camera.

An important factor in choosing a lens is focus length. This generally refers to the length of the lens itself, and is measured in millimeters. A 50 mm lens is considered average, good for shooting subjects that are 33 to 65 feet (10 to 20 meters) from the camera. Wide angle lenses have shorter focal lengths that can capture large panoramic scenes or large subjects that are relatively close to you. Telephoto lens, which can have focal lengths of hundreds of millimeters, are basically telescopes mounted to a camera. They make far away subjects seem closer, but with a limited field of view.

If the choice of lens focal length is getting too confusing, maybe you should keep it simple. If your camera has a zoom lens, then the focal length changes as you zoom in and out. Remember to never use digital zoom — the camera is simply enlarging the pixels to make the subject seem closer, which reduces image quality.

So far we've talked about aperture, which defines how much light gets through, and ISO number, which determines the light sensitivity of the camera sensors. Shutter speed is the third part of the exposure triangle. It refers to how long the shutter remains open to allow light through. Shutter speeds are given in fractions of a second — you'll commonly shoot at 1/500.

Shutter speed is tricky because slow shutter speeds don't just allow more light through, they can cause blurring. The entire time the shutter is open, the light source is hitting the image sensor, and if an object (or the camera itself) moves during that time, the movement will show up as a blur. If you've ever seen one of those photographs of the stars at night showing the lines of their motion as the Earth rotates, that image was the result of a very long shutter speed recording the starlight over several hours.

You can reduce blur by using a tripod to hold the camera steady when you shoot, which lets you use slower shutter speeds, but if you're shooting sports and you don't want blurry players, that only helps so much.

White balance reveals an interesting difference between a digital camera and a human eye: A human eye has a human brain attached. When you look at a white object, your brain is actually interpreting the lighting cues around you and calculating that the object is white on the fly. If the object is under a blue light, it will really look blue, but your brain compensates for the color difference, so you'll see it as white. The camera does no such compensating unless you force it to do so, so if a white object is under a bluish light, the camera will record bluish pixels.

Adjusting white balance helps force the camera to compensate for the fact that most lighting conditions aren't perfectly white. Many indoor lights have a yellowish tinge to them, while fluorescent lights have a bluish tint. Even natural light is a little bluer than you might think. You can set white balance manually by adjusting it up or down or selecting the appropriate setting, then taking some test shots to see which ones look most natural.

Alternately, you can use a camera's automatic white balance function. Just aim the camera at a white object, such as a large sheet of paper (this is why news vans are almost always white — so the camera operator has an easy way to set white balance). When you hit the white balance button, the camera will automatically adjust to the lighting conditions.

With digital photography, your work doesn't end when the photo is taken. While Photoshop is the most famous photo processing software package, there are dozens more that can be used to alter and manipulate photos. With practice, you can use them for a lot more than pasting photos of your little sister's face onto zoo animals.

Beginners can use post processing to adjust brightness, contrast, and color balance. Post processing is an easy way to make a poor photo passable and make a good photo look great. More advanced users can play with color channels, apply special effects or make a composite of multiple photos. For example, if you were bracketing a shot of a dog in front of a window, you might get one photo with the dog properly exposed but the window too bright, and one with the window exposed but the dog too dark. In post processing, you could combine the two for one perfectly exposed image.

While there's no limit to the creative things you can do with post processing software, there's a reason this term is last on the list. Learn to shoot excellent photos with your digital camera first.

By mastering the practice of image stabilization, focal length, and troubleshooting a variety of image sensor and camera setting issues, you'll improve your image quality. Then you'll have the raw materials to do good post processing work later.