In: Physics
On this “Living Planet” that we call Earth, there are lots of interesting events that take place. These events are around us, which we see or do or experience regularly. At some point in time, your curiosity would have pushed you to ask questions about what’s going on? How does that happen? Well, leaving miracles apart, the answer to all these questions is “Physics.” In fact, Physics governs our everyday lives in one way or the other. A camera is an optical instrument used to record images. 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.
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).