Types of Lenses
Normal lenses, also called standard lenses, are the lenses that have come with basic SLR camera setups for many years. The image these standard lenses “see” is about the same size in the viewfinder as the image the human eye sees. Wide-angle lenses have shorter focal lengths and cover a wider angle of view than normal and telephoto lenses do, and also capture a wider field of view than the human eye can. Telephoto lenses have longer focal lengths and smaller angles of view; they make subjects in the distance look closer and larger.
A standard lens for a 35mm camera is typically 50mm, although lenses that range from 45mm to 55mm are also considered within the normal or standard range. A 50mm lens covers a 45° angle of view. Normal lenses are also called prime lenses because they have fixed focal lengths. In the hands of a new photographer, normal lenses capture the images without the distortion a wide-angle or telephoto lens causes. Pictures taken with them look very natural and familiar, which makes these lenses a favorite of many photographers.
Normal lenses are generally very fast and can have maximum apertures as large as f/1.2. This makes them great for low-light situations, especially for taking action pictures in less-than-perfect light.
Like all prime lenses, you can't adjust image size with a normal lens alone. To make images bigger or smaller, you have to move the camera closer or farther away from the subject. When shooting with large apertures, the depth of field on normal lenses is fairly shallow, so accurate focusing is essential.
Wide-angle lenses have shorter focal lengths and cover a wider angle of view than normal and telephoto lenses do. For 35mm cameras, they range from 13mm to 35mm, with 28mm considered a standard wide-angle lens. The shortest wide-angle lenses have the greatest angle of view, starting with 118° for a 13mm lens and going to 63° on a 35mm lens.
There's also a special wide-angle lens called a fish-eye with an extremely short focal length (beginning at 6mm) and an extremely wide angle of view (220°). They create round, distorted images that look like they're viewed through the eyes of a fish. These lenses make distant objects appear smaller, near objects seem larger, and the distance between objects look greater.
Advantages of Wide-Angle Lenses
Wide-angle lenses are definitely the lens of choice in cramped conditions, such as small rooms or other situations where you can't back up far enough to include everything you want in the picture if you use a normal lens. Their wider field of view makes them great for scenic outdoor photography as well, especially if your subject is a sweeping panorama and you want to get as much of it as you can in your shot.
Wide-angle lenses make nearby objects look really big and distant ones really small, so the classic gimmick shot of a person holding a building in his hand is created with a wide-angle lens. They're also good when you want to use perspective for emphasis, such as when exaggerating the space between objects will add to the picture's interest.
What lens do I need for closeup photography?
Normal or telephoto lenses that can focus extremely close can be used for closeup work. You can buy macro lenses with focal lengths that can also be used as normal or telephoto lenses, or regular lenses with macro capabilities. You can also use an extension tube, which mounts between the camera body and the lens to move the lens closer to the subject.
Disadvantages of Wide-Angle Lenses
It is easy to get distorted images with wide-angle lenses, which makes them inappropriate for taking closeups of people. Wide-angle lenses used for closeups will distort the faces of your subjects. They make the features closest to the lens (like noses) bigger and those farther away from the lens (ears, for instance) smaller. Because they capture more of a scene, people and objects at the edges of wide-angle shots can also appear distorted. This actually happens with all lenses to a certain degree, but it's not nearly as noticeable with telephoto and normal lenses. Wide-angle lenses make it more obvious to the picture-viewer's eye.
Another problem with wide-angle lenses is something called keystoning, a phenomenon in which parallel vertical lines on buildings or other subjects look like they're converging. You can avoid keystoning by keeping your camera facing straight forward — not tipping it up or down — unless you want to deliberately create this affect. Keystoning can be corrected in digital darkrooms.
Telephoto lenses are basically the opposite of wide-angle lenses. Since they have longer focal lengths and smaller angles of view, they make subjects look closer and larger. They're great for when you want to get a good shot but can't get close enough to your subject to use a normal lens. Since they have shallow depth of field, they're also good for focusing more attention on the main subject of a picture by eliminating distracting backgrounds and foregrounds. For 35mm cameras, telephoto lenses range from 85mm up to 2000mm, with corresponding angles of view from 28° to an amazingly small 1°.
Advantages of Telephoto Lenses
The most obvious advantage of using a telephoto lens is to make faraway objects look bigger. A 100mm telephoto lens will double the size of the image produced by a 50mm lens; a 500mm telephoto lens will make the same image ten times larger. Because they don't exaggerate the distance between objects — in fact, they compress it — telephoto lenses don't distort features, making medium-range telephoto lenses good for portrait work, because you can shoot at a greater distance. With telephoto lenses, perspective is less apparent because of the narrow field of view. Distant objects, enlarged and more visible with a telephoto, show less divergence and convergence of lines, but the perspective, albeit reduced, is still there.
Telephoto lenses are often used to create photographic compression. Using an extreme telephoto on a distant scene of repeating, overlapping shapes, such as cars on a highway, will make them look closer to each other than they actually are. The narrow angle of view on these lenses is great for cropping out parts of a scene you don't want to include.
Disadvantages of Telephoto Lenses
Since telephoto lenses magnify their subjects, they must be held perfectly still when the shutter is snapped. If they're not, pictures will be blurry as the magnification of the lens also magnifies any movement of the camera. Getting good photos with telephoto lenses often requires using a tripod and a cable release — especially if the lens is longer than 400mm — or a self-timer if your camera doesn't have a cable-release feature. Using fast shutter speeds will help minimize camera shake and subject movement, which is also exaggerated because of the magnification. New cameras with Image Stabilization technology (IS) help to minimize the blurring effect so typical in telephoto shots and are available in both film and digital cameras.
These extremely versatile and popular lenses combine features of the other lenses into one handy piece of equipment. By adjusting a collar on the lens or pressing a zoom button on a point-and-shoot model, you can change focal lengths, make images look larger or smaller, and change your angle of view. For example, a 28mm–70mm zoom will adjust from the wide-angle focal length of 28mm to a slight telephoto length of 70mm.
Zoom lenses come in various focal length ranges. The most common are 28mm–50mm or 21–50mm, covering a wide-angle to normal range; 35mm–105mm or 35mm–135mm, which increases the focal length to the telephoto range; and 80mm–200mm, the medium to full telephoto lenses.
Early zoom lenses were notoriously awkward to use and quite heavy. They also weren't as sharp as fixed-focus lenses. Manufacturers now claim that advances in design and materials have made zoom lenses as sharp as primes. If you never enlarge your images to more than 5″ × 7″, you won't have to worry that much about the difference in sharpness between zoom lenses and prime lenses. Digital users of telephotos can sharpen a slightly blurry image in their digital darkroom.
Zoom lenses are labeled with their minimum and maximum focal lengths, followed by the largest aperture available at each extreme, such as 75mm–300mm f/4–5.6. When you're zoomed out to 20mm (very wide angle) your largest f-stop is f/3.5. As you zoom in toward normal or telephoto, the largest aperture changes from f/3.5 to f/4.5, which means it lets in less light.
Advantages of Zoom Lenses
The greatest advantage of zoom lenses is their convenience; they can keep you from having to buy lots of prime lenses. They also make it possible for you to make images larger or smaller without having to change lenses or shooting position — all you have to do is adjust the focal length. This makes it easier to compose the perfect shot.
Disadvantages of Zoom Lenses
Zoom lenses — especially big telephoto zooms — are heavier than other lenses. They're also more expensive — although expense is relative. It
Perhaps the most serious drawback to zoom lenses is that they're slower than other lenses. Buying a zoom with an aperture wider than f/4 usually entails a pretty hefty investment. Because the maximum aperture gets smaller as the focal length gets longer, it can be difficult to use fast shutter speeds. Focusing is also trickier because less light reaches the focusing screen.
Some zoom lenses can also change focus as you zoom. This means that if you zoom in (move to the telephoto setting) to focus and then zoom out, the image may need to be refocused at the new focal length. Autofocus zooms take care of this if there is enough light for the system to work.