Camera lenses are manufactured in a wide variety of focal lengths and are labeled according to their focal length, usually expressed in millimeters (mm).
Prime Lens
A prime lens is a lens that has a fixed focal length, as opposed to a zoom lens (which has an adjustable focal length). A prime lens of a given focal length does not give as much option as a zoom lens that includes that focal length, but the prime lens is often of a superior optical quality (means it gives better picture quality though technology has made this minimal). It is lighter, smaller and cost less in comparison with a zoom lens. Prime lens usually have larger maximum aperture (smaller f-numbers) which allow photography in less light and a shallower depth of field. They also suffer from fewer problems related to chromatic aberrations because they have fewer moving parts.
Normal Lens
The most common lens or what is referred to as a normal focal length lens on a 35mm format is the 55mm lens. This lens is referred to as a normal focal length because it covers an angle of view which is similar to that of the human eye. These lenses have the capability of recording a very deep depth of field, with objects very close to the camera to infinity in sharp focus when your lens aperture is squeezed down to f 16 or f 22.
Wide Angle Lens (Landscape)
Shorter focal length lenses, like 24 and 28mm lenses, are known as wide angle lenses because their angle of view is wider than the human eye. These lenses are used primarily for pictorial photographs or if you are working in a confined area and can’t step back far enough to take your shot. They are wonderful for getting close to your subject; they also allow you to fit more into the frame for compelling landscape shots.
To avoid distortion wide angle lenses should be held level and not tilted up or down. However you can create some interesting shots when you tilt a wide angle lens up or down and deliberately distort your subjects.
Telephoto Lens (Sports)
Longer focal length, the physical length of the lens is shorter than the focal length. These lens are for taking picture of faraway subjects that might be difficult to reach, they allow you to zoom in much more than a standard lens. You will generally get 4 x magnification or more.
Telephoto lenses are sometimes broken into the further sub-types of medium telephoto: lenses covering between a 85mm to 135mm in 35mm film format, long telephoto: lenses covering between a 135mm to 300mm in 35mm film format and super telephoto: lenses covering over 300mm in 35mm film format.
You can also use telephoto lens for taking pictures of faces when you zoom in as far as you can, it flattens facial features and make people’s faces look nicer as long as their faces are clean.
Macro Lens
Macro lenses are designed for extreme close-up work, with a long barrel for close focusing. Such lenses are popular for nature shooting such as small flowers, and are one of the most common tools for macro photography. Most of these lenses can focus to infinity and tend to be quite sharp. Macro lenses of different focal lengths find different uses;
Continuously Variable Focal Length: Suitable for virtually all macro subjects;
45–65 mm: Product photography, small objects that can be approached closely without causing undesirable influence, and scenes requiring natural background perspective;
90–105 mm: Insects, flowers, and small objects from a comfortable distance;
150–200 mm: Insects and other small animals where additional working distance is required.
Depth of field is extremely small when focusing on close objects. A small aperture (high f-number) is often required to produce acceptable sharpness across a three-dimensional subject. This requires a slow shutter speed, brilliant lighting, or a high ISO.
Fish Eye Lens
A fish-eye lens is a wide-angle lens that takes in a broad, panoramic and hemispherical image. They give a unique, distorted appearance. They are often used by photographers shooting broad landscapes to suggest the curve of the Earth. The focal lengths of fish-eye lenses depend on the film format. For the popular 35 mm film format, typical focal lengths of fisheye lenses are between 8 mm and 10 mm for circular images, and 15–16 mm for full-frame images.
Optical image stabilization
Image stabilization is a technique used to reduce image blur caused by the camera not being held steady. There are two kinds of image stabilization used in DSLR cameras and their lenses
In-body image stabilization is implemented by moving the image sensor in an attempt to counteract the sensed motion of the camera. The advantage of this technique is that it works for all lenses mounted on the camera, at least if the camera electronics are aware of the lens’ focal length. This is most commonly done automatically, but some cameras allow the user to input the focal length manually for use with lenses with no electronic coupling.
In-lens image stabilization is implemented in the lens itself, and moves the lens elements in an attempt to counteract the sensed motion of the camera. The inherent advantage of this kind of image stabilization is that it steadies the viewfinder image, allowing for more accurate framing and autofocus. The disadvantage is that you have to pay the extra cost for every lens you buy for which you want image stabilization.
The effectiveness of image stabilization systems varies somewhat from implementation to implementation, but there seems to be no inherent superiority to either lens-based or sensor-based systems as far as the actual improvement in captured images.
References
http://www.typesofcameralenses.com
