Question

Cameras have various mechanisms to control how the light falls onto the light-sensitive surface. Lenses focus the light entering the camera, the size of the aperture can be widened or narrowed to let more or less light into the camera, and a shutter mechanism determines the amount of time the photosensitive surface is exposed to the light.

- Write a short report in 5 pages (Word File) about how a camera is used as an optical instrument used to record images and support your report by several pictures and references.

Answer 1

A camera is an optical instrument used to record images. At their most basic, cameras are sealed boxes (the camera body) with a small hole (the aperture) that allow light in to capture an image on a light-sensitive
surface (usually photographic film or a digital sensor). Cameras have various mechanisms to control how the light falls onto the light-sensitive surface. Lenses focus the light entering the camera,
the size of the aperture can be widened or narrowed to let more or less light into the camera, and a shutter mechanism determines the amount of time the photo-sensitive surface is exposed to the light.

image of a camera

The still image camera is the main instrument in the art of photography and captured images may be reproduced later as a part of the process of photography, digital imaging, photographic printing.
The similar artistic fields in the moving image camera domain are film, videography, and cinematography.

The word camera comes from camera obscura, which means "dark chamber" and is the Latin name of the original device for projecting an image of external reality onto a flat surface. The modern photographic
camera evolved from the camera obscura. The functioning of the camera is very similar to the functioning of the human eye. The first permanent photograph was made in 1825 by Joseph Nicéphore Niépce.

interior of camera

Mechanics

A camera captures light photons, usually from the visible spectrum for human viewing, but in general could also be from other portions of the electromagnetic spectrum. All cameras use the same basic design: light
enters an enclosed box through a converging or convex lens and an image is recorded on a light-sensitive medium (mainly a transition metal-halide). A shutter mechanism controls the length of time that light
can enter the camera.

Most cameras also have a viewfinder, which shows the scene to be recorded, and the ability to control focus and exposure so that it is not too bright or too dim.

Exposure control

Different apertures of a lens
The aperture, sometimes called the diaphragm or iris, is the opening through which light enters the camera. Typically located in the lens, this opening can be widened or narrowed to control the amount of light
that strikes the film. The aperture is controlled by the movements of overlapping plates or blades that rotate together and apart to shrink and expand the hole at the center.The diameter of the aperture can be set
manually, typically by adjusting a dial on the camera body or lens, or automatically based on calculations influenced by an internal light meter.

forcal plane shutter

The size of the opening is set at standard increments, typically called "f-stops" (but also "f-numbers", "stop numbers", or simply "steps" or "stops"), that usually range from f/1.4 to f/32 in standard increments:
1.4, 2, 2.8, 4, 5.6, 8, 11, 16, 22, and 32.[4] As the numbers increase, each increment (or "stop") halves the amount of light entering the camera. Conversely, the lower the number, the larger the opening, and so the
more light that is let into the camera.

The wider opening at the lower f-stops narrows the range of focus so the background of an image is blurry when focusing on the foreground, and vice-versa. This "depth of field" increases as the aperture closes, so
that objects that are at differing distances from the camera can both be in focus; when the aperture is at its narrowest, the foreground and background are both in sharp focus.

Shutter
The shutter, along with the aperture, is one of two ways to control the amount of light entering the camera. The shutter determines the duration that the light-sensitive surface is exposed to light. The shutter
is opened, light enters the camera and exposes the film or sensor to light, and then the shutter closes. There are two types of mechanical shutters. The leaf-type uses a circular iris diaphragm maintained under
spring tension inside or just behind the lens that rapidly opens and closes when the shutter is released. A focal-plane shutter. In this shutter, the metal shutter blades travel vertically.

Digital cameras may use one of these types of mechanical shutters or they may use an electronic shutter, the type used in the cameras of smartphones. Electronic shutters either record data from the entire sensor
at the same time (a global shutter) or record the data line by line across the sensor (a rolling shutter). In movie cameras, a rotary shutter opens and closes in sync with the advancing of each frame of film.

The duration is called the shutter speed or exposure time. The longer the shutter speed, the slower it is. Typical exposure times can range from one second to 1/1,000 of a second, though durations longer and shorter
han this are not uncommon. In the early stages of photography, exposures were often several minutes long. These long exposure times often result in blurry images, as a single object is recorded in multiple places
across a single image for the duration of the exposure. To prevent this, shorter exposure times can be used. Very short exposure times can capture fast-moving action and completely eliminate motion blur.

Like aperture settings, exposure times increment in powers of two. The two settings determine the exposure value (EV), a measure of how much light is recorded during the exposure. There is a direct relationship
between the exposure times and aperture settings so that if the exposure time is lengthened one step, but the aperture opening is also narrowed one step, the amount of light exposing the film or sensor is the same.

Lens
The lens of a camera captures the light from the subject and brings it to a focus on the sensor. The design and manufacture of the lens is critical to the quality of the photograph being taken. The technological
revolution in camera design in the 19th century revolutionized optical glass manufacture and lens design with great benefits for modern lens manufacture in a wide range of optical instruments from reading glasses
to microscopes. Pioneers included Zeiss and Leitz.

Camera lenses are made in a wide range of focal lengths. They range from extreme wide angle, and standard, medium telephoto. Each lens is best suited to 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.

Focus
The distance range in which objects appear clear and sharp, called depth of field, can be adjusted by many cameras. This allows for 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 metres (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).