The Camera


The camera is basically a light-tight box  - to house the film  - equipped with a lens. The lens is necessary to produce a sharp image on the film or disk.

Film cameras are divided into four main groups:

 
 
1.

The Direct Vision Finder Camera
These cameras are equipped with an optical finder, but the angle of view is slightly bigger than that of the camera. The view of the camera is outlined by a white frame. The biggest disadvantage of these cameras is that the eye does not see what the camera 'sees'. A dirty lens or an unremoved lens cap is only seen on the final print.
Most of the modern cameras are equipped with an 'auto exposure' system and are very popular amongst amateur photographers.
 

2. The Twin Lens Reflex Camera (TLR)
The twin lens reflex camera is two cameras in one body. One camera is used for framing the picture and for focusing; the other for the actual photography. Most twin lens reflex cameras use 120 film and produce square negatives of 6 x 6 cm. They are not popular any more.
 
3. The Single Lens Reflex Camera (SLR)
This is the most popular camera design and most single lens reflex cameras use 35mm film. A single lens is used for viewing the image and for the actual photography. A hinged mirror behind the lens reflects the image via a pentaprism to the eye of the photographer. When the shutter release is pressed, the mirror swings out of the way so that the film can be exposed.
 
4. The Technical or Studio Camera
Most of these cameras are large-format cameras for film sizes of 9 x 12 cm and bigger and are used mainly by professional photographers.
 
5. Camera Controls
It is important for a photographer to be familiar with the position and function of the controls of the camera. Consult the camera manual if you use a camera for the first time.
Two vital controls on the camera are the aperture setting, also called the f-stop and the shutter speed control. These two settings control the amount of light that reach the film.
  • The Aperture

  • The aperture (lens opening), also called the f-stop, works like the pupil of the eye. It can be opened and closed by turning the f-stop ring on the lens. Typical values are 1.4, 2, 2.8, 4, 5.6, 8, 11, 16, 22 and 32.
    These numbers refer to the relation between the diameter of the hole and the focal length of the lens and should be read 1:8 or 1:11. This means that an aperture of f8 on a 50mm lens has a diameter of 50/8 = 6,25 mm. An aperture of f8 on a 200 mm lens has a diameter of 200/8 = 25 mm. Thus f8 on a 50 mm lens is smaller than f8 on a 200 mm lens. The apertures are designed so that each subsequent aperture lets in half as much light as the one before.
    The aperture does not only determine the amount of light that falls on the film, but also influences the depth of field. A small lens opening, say f16 will cause more fore- and background to be in focus than a lens opening of f4.
     
  • The Shutter Speed

  • All cameras are equipped with a shutter, either a diaphragm shutter or a focal plane shutter. Diaphragm shutters are situated between the elements of the lens and consist of three or more thin metal blades. Focal plane shutters are situated just in front of the film and consist of slatted metal or opaque fabric blinds. The blinds form a slit through which light passes onto the film while the slit passes across the film.
    The amount of light that reaches the film is controlled by the time the camera shutter stays open - 1 s, 1/2 s, 1/4 s . . . 1/2000 s. Each time setting is half the time of the setting before. The shutter speed is also used to indicate or freeze movement. A fast moving object will produce a blurred image on film if taken with a slow shutter speed.
    To prevent camera shake it is best to use a shutter speed faster than the reciprocal of the focal length of the lens. Example: with a 50 mm lens use speeds faster than 1/60 s, with a 100 mm lens use speeds faster than 1/125 s. For slower speeds use a tripod or bean bag.
     
  • The Exposure Meter
    Most cameras today have a built-in exposure meter. The exposure meter indicates suitable lens opening and shutter speed settings for a given film. Set the film speed (ISO, ASA or DIN) on the camera, otherwise the exposure meter reading will be incorrect. Exposure meters are calibrated to expose film to yield an average density of 0,74. This should give a middle grey on a positive print and match the grey of a 'grey card'.
    A 'grey card' is a 20 x 25 cm piece of neutral grey cardboard that reflects 18% of the light falling on it. It is a handy tool to determine exposure, lighting ratios and colour balance. In the 'Zone System' the range of grey tones, from black to white, is divided into 11 Zones. Black is referred to as Zone 0, white as Zone X and middle grey as Zone V.
  • Modern cameras are equipped with sophisticated electronic circuits and will not function when the battery is flat. It is advisable to have spare batteries handy.

 

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