Views: 19
LIGHT, LENS AND IMAGES
Light travels in a straight line, buts it is often dispersed as it passes through different surfaces and mediums. These causes light to produce dim or sometimes ill-defined images. However, in order to produce brighter and sharper images, it is necessary to gather more light and gather it or converge the light rays at one point to focus the image. This requires a lens.
The lens of a camera captures the light from the subject and brings it to a focus on the film or detector. The design and manufacture of the lens is critical to the quality of the photograph being taken. Lenses converge light by bending them (diffraction) to one point by simply transmitting light from each part of the object then focusing it on a flat surface i.e. film which is always placed on the opposite site of the receiving surface.
Camera lenses are made in a wide range of focal lengths. They range from extreme wide angle, wide angle, standard, medium telephoto and telephoto. Each lens is best suited a certain type of photography. The extreme wide angle may be preferred for architecture because it has the capacity to capture a wide view of a building. The normal lens, because it often has a wide aperture, is often used for street and documentary photography. The telephoto lens is useful for sports and wildlife but it is more susceptible to camera shake.
Types of camera lenses
There are two basic categories of camera lenses:
- Prime lenses.Primes have a fixed lens focal length, making them faster and sharper. While prime lenses are less flexible due to the fixed focal length, they are also fast and lightweight, making them easy to travel with
- Zoom lenses.Zooms use a series of lenses to allow different focal lengths from a single lens, making them more flexible but not as fast. They contain more glass, which aids in their flexibility, but they also tend to be bigger and heavier than prime lenses.
Within both prime and zoom types of lenses, there are a variety of lenses, all with different focal lengths.
- Macro Lenses
This type of camera lens is used to create very close-up, macro photographs. They have a unique design that allows them to produce sharp images at extremely close range. These lenses are great for nature photography, enabling you to capture an enormous amount of detail in one image.
- Telephoto Lenses
Telephoto lenses are a type of zoom lens with multiple focal points. These types of lenses are great for isolating a subject that is far away. However, such great magnification comes at the price of a narrower field of view. In the same way that you would use a telescope to look at stars and planets, a telephoto lens is used for focusing in on distant objects. Many sports photographers use telephoto lenses to provide a sense of intimacy with the subjects on the field (the players) while standing on the sidelines or in the bleachers. There are many different types of telephoto lenses, and some can be quite large, heavy, and expensive, so take some time in choosing the right telephoto lens.
- Wide Angle Lenses
Wide angle lenses are ideal for fitting a large area into your frame. This is especially useful for landscape photography or street photography. With wide angle lenses, almost everything is in focus, unless your subject is very close to the lens.
- Standard Lenses
Standard lenses can be used for a variety of different types of photography. Their focal lengths fall somewhere in the middle, usually between 35mm and 85mm. A zoom lens within this range will have a small enough focal length at the bottom end to take a wider angle, full-frame photo, and a large enough focal length at the top end to zoom in on subjects.
- Specialty Lenses
Finally, there are some more specialized camera lenses that can impart a unique look and feel to your photographs. There are several types of specialty camera lenses, but a few of the most prominent examples are:
Fisheye lens.
A fisheye lens is an ultra-wide-angle lens that can take in a full 180 degree radius around it. Fisheye lenses are so named because they distort an image’s field of view, making even a room in a house look like a bubble.
Tilt shift lens. A tilt shift lens distorts perspective, making things look smaller than they really are—almost as if they are toys.
Infrared lens. These lenses play with light rather than perspective, filtering out all light waves except infrared for a unique visual effect.
Focus
The distance range in which objects appear clear and sharp, called depth of field, can be adjusted by many cameras. This allows a photographer to control which objects appear in focus, and which do not.
Due to the optical properties of photographic lenses, only objects within a limited range of distances from the camera will be reproduced clearly. The process of adjusting this range is known as changing the camera’s focus. There are various ways of focusing a camera accurately. The simplest cameras have fixed focus and use a small aperture and wide-angle lens to ensure that everything within a certain range of distance from the lens, usually around 3 meters (10 ft.) to infinity, is in reasonable focus. Fixed focus cameras are usually inexpensive types, such as single-use cameras. The camera can also have a limited focusing range or scale-focus that is indicated on the camera body. The user will guess or calculate the distance to the subject and adjust the focus accordingly. On some cameras, this is indicated by symbols (head-and-shoulders; two people standing upright; one tree; mountains).
Rangefinder cameras allow the distance to objects to be measured by means of a coupled parallax unit on top of the camera, allowing the focus to be set with accuracy. Single-lens reflex cameras allow the photographer to determine the focus and composition visually using the objective lens and a moving mirror to project the image onto a ground glass or plastic micro-prism screen. Twin-lens reflex cameras use an objective lens and a focusing lens unit (usually identical to the objective lens.) in a parallel body for composition and focusing. View cameras use a ground glass screen, which is removed and replaced by either a photographic plate or a reusable holder containing sheet film before exposure. Modern cameras often offer autofocus systems to focus the camera automatically by a variety of methods