Camera
[Film Technology]
A roll of film is
pulled down for perforations at a
time, by a claw movement. As the claw disengages, the film is held
steady by a spring loaded back plate, and in some cameras an extremely
precisely- fitting register pins which
moves in to the perforations and
ensures that each frame is
located in exactly the same way. Once the film is stationary the shutter opens
and the frame is
exposed. The shutter is a continuously rotating disc with
alternative segments cut away to allow the passage of light. By changing the
angle of segment that is cut away, a longer exposure time or shorter exposure time is
possible; usually the shutter is 180° open
and 180° close allowing 1/48th of a second between exposures for
the claw to pull the film down. In a reflex camera the
shutter is silvered [silvered shutter], and when closed, reflects light into the viewfinder, giving cameraman exactly
the same view as the film in the film gate. 16 mm cameras do not use register pin; the resultant image is
nevertheless steady enough for all general work. Some times the sound recorder will
also be called as camera by its people. The camera does not much more than just
‘take a picture’ of a situation. It gives the audience a
certain impression of a subject and its surroundings. Camera[still]- Modern cameras operate on the
basic principle of the camera obscura. Light passing through a tiny hole, or aperture, into an otherwise light-proof box casts
an image on the surface opposite the aperture. The addition of a lens sharpens
the image, and film makes
possible a fixed, reproducible image. The camera is the mechanism by which film
can be exposed in a controlled manner. Although they differ in structural
details, modern cameras consist of four basic components: camera body, shutter, diaphragm, and lens. Located in the body is a light-proof chamber (Latin, camera) in which film is held and exposed. Also
in the body, located opposite the film and behind the lens, are the diaphragm and shutter. The lens, which is attached to the front of the
body, is actually a grouping of optical glass lenses. Housed in a metal ring or cylinder [focusing ring. Focusing cylinder], it allows the photographer to focus an
image on the film. The lens may be fixed in place or set in a movable mount.
Objects located at various distances from the camera can be brought into sharp
focus by adjusting the distance between the lens and the film. The diaphragm, a circular aperture behind the lens,
operates in conjunction with the shutter to
admit light into the light-proof chamber. This opening may be fixed, as in many amateur cameras, or it may be adjustable. Adjustable diaphragms are
composed of overlapping strips of metal or plastic that, when spread apart,
form an opening of the same diameter as the lens; when meshed together, they
form a small opening behind the centre of the lens. The aperture openings correspond to numerical settings, called f-stops, on the camera or the lens. The shutter, a spring-activated mechanical device,
keeps light from entering the camera except during the interval of exposure.
Most modern cameras have focal-plane shutter or leaf shutters. Some older amateur cameras use a drop-blade shutter, consisting of a hinged piece that, when
released, pulls across the diaphragm opening and exposes the film for about
1/30th of a second. In the leaf shutter, at the moment of exposure, a cluster of
meshed blades springs apart to uncover the full lens aperture and then springs
shut. The focal-plane shutter consists
of a black shade with a variable-size slit across its width. When released, the
shade moves quickly across the film, exposing it progressively as the slit
moves. Most modern cameras also have some sort of viewing system or viewfinder to
enable the photographer to see, through the lens of the camera, the scene being
photographed. Single-lens reflex cameras (SLRs) all incorporate this design feature, and
almost all general-use cameras have some form of focusing system as well as a film-advance mechanism. Camera
Designs - Cameras come in a
variety of configurations and sizes. The first cameras, “pinhole” cameras, had no lens. The flow of light was
controlled simply by blocking the pinhole. The first camera in general use, the box camera, consists of a wooden or plastic box with
a simple lens and a drop-blade shutter at
one end and a holder for roll film at the other. The box camera is equipped
with a simple viewfinder that shows the extent of the picture area; some models
have, in addition, one or two diaphragm apertures and
a simple focusing device. The view camera, used primarily by professionals, is the
camera closest in design to early cameras that is still in widespread use.
Despite the unique capability of the view camera, however, other camera types,
because of their greater versatility, are more commonly used by both amateurs
and professional cameras. Chief among these are the single-lens reflex, twin-lens reflex (TLR), and rangefinder. Most SLR and rangefinder cameras use the 35-mm film format, while most
TLR as well as some SLR and rangefinder cameras use medium-format film, that is, size 120 or 220. -View Cameras -View cameras are generally larger
and heavier than medium- and small-format cameras and are most often used for studio photograph, landscape photograph, and architectural photography. These cameras use large-format films that
produce either negatives or transparencies with
far greater detail and sharpness than
smaller format film. View cameras have a metal or wooden base with a geared
track on which two metal standards ride,
one at the front and one at the back, connected by a bellows. The front standard contains
the lens and shutter; the rear standard holds
a framed ground-glass panel, in front of which the film holder is
inserted. The body configuration of the view camera, unlike that of most
general-purpose cameras, is adjustable. The front and rear standards can be
shifted, tilted, raised, or swung, allowing the photographer unparalleled
control of perspective and focus. Rangefinder Cameras -
Rangefinder cameras have a viewfinder through
which the photographer sees and frames the subject or scene. The viewfinder does not, however, show
the scene through the lens but instead closely approximates what the lens would
record. This situation, in which the point of view of
the lens does not match that of the viewfinder, results in what is known as parallax. At longer distances, the effects of
parallax are negligible; at short distances, they become more pronounced,
making it difficult for the photographer to frame a scene or subject with
certainty. Reflex Cameras --Reflex
cameras, both the SLR and the TLR types, are equipped with mirrors that
reflect in the viewfinder the
scene to be photographed. The twin-lens reflex is
box-shaped, with a viewfinder consisting of a horizontal ground-glass screen located
at the top of the camera. Mounted vertically on the front panel of the camera
are two lenses, one for taking photographs and the other for viewing. The
lenses are coupled, so that focusing one automatically focuses the other. The
image formed by the upper, or viewing, lens is reflected to the viewing screen by a
fixed mirror mounted at a 45° angle. The photographer focuses the camera and
adjusts the composition while looking at the screen. The image formed by the lower lens is
focused on the film at the back of the camera. Like rangefinder cameras, TLRs
are subject to parallax. In the SLR type of reflex camera, a single lens is used for both viewing
the scene and taking the photograph. A hinged mirror situated between the lens
and the film reflects the image formed by the lens through a five-sided prism and
on to a ground-glass screen on
top of the camera. At the moment the shutter is opened, a spring automatically
pulls the mirror out of the path between lens and film. Because of the prism, the image recorded on the film is almost
exactly that which the camera lens “sees”, without any parallax effects. Most SLRs are precision
instruments equipped with focal-plane shutters. Many have automatic exposure-control features
and built-in light meters. Most modern SLRs have electronically triggered shutters; apertures, too, may be electronically
actuated or they may be adjusted manually. Increasingly, camera manufacturers
produce SLRs with
automatic focusing, an innovation originally reserved for amateur cameras.
Minolta's Maxxum series, Canon's EOS series, and Nikon's advanced professional
camera, the F-4, all have autofocus capability
and are completely electronic. Central processing units (CPUs) control the electronic functions in
these cameras. Minolta's Maxxum 7000i has
software “cards” which, when inserted in a slot on the side of the camera,
expand the camera's capabilities. Autofocus cameras use
electronics and a CPU to sample automatically the distance between camera and
subject and to determine the optimum exposure level. Most autofocus cameras bounce either an infrared light beam or ultrasonic (sonar) waves off
the subject to determine distance and set the focus. Some cameras, including
Canon's EOS and Nikon's SLRs, use passive autofocus systems. Instead of emitting waves or beams, these cameras automatically adjust the
focus of the lens until sensors detect
the area of maximum contrast in a
rectangular target at the centre of the focusing screen. Design
Comparisons- Of
the three most widely used designs, the SLR is the most popular among both
professionals and amateurs. Its greatest advantage is that the image seen
through the viewfinder is virtually identical with that on which the lens is
focused. In addition, the SLR is generally easy and fast to operate and comes
with a greater variety of interchangeable lenses and interchangeable accessories than
the other two camera types. The rangefinder camera, previously used by photojournalists because
of its compact size and ease of operation (compared with the big, slow 4 x 5 in
press cameras used by an earlier generation) has largely been replaced by the SLR. Rangefinder cameras, however, have a simpler optical system with
fewer moving parts and are thus inherently more rugged than SLRs, in addition
to being quieter and weighing less. For these reasons, some photographers,
mainly professionals, continue to use them. Compared with the other two
designs, TLRs have a relatively slow focusing system. As with rangefinder cameras, fewer
interchangeable lenses are available, yet the TLR remains popular. The camera
produces larger negatives than most SLRs and rangefinders, an advantage when
fine detail must be rendered in the final image (the Apollo astronauts used Hasselblad TLRs on
the Moon). In recognition of this, some manufacturers, including Hasselblad, Mamiya, Bronica, and Rollei, have combined the convenience of the SLR
with the medium-film format, further reducing the market for the TLR.
Some cameras are designed primarily for amateurs: they are simple to operate,
and they produce photographs acceptable to the average snapshot photographer. Many “point-and-shoot” amateur cameras now
employ sophisticated technology, with features such as autofocus and exposure control systems that simplify the process of
taking pictures and almost guarantee good-quality photos, while still limiting
photographer control.
