The advanced camera

The advanced camera
For serious photography you require a camera that offers you full control over apperture, focusing and shutter speeds, and preferably a camera to which you can fit a number of different lenses. Most amateurs and many professionals work in the 35mm format, in which the choice of cameras and accessories in unrivaled.

The single – lens reflex camera
By far the most widely sold type of 35mm camera is the single – lens reflex (SLR) camera. In this type the light coming through the taking lens in reflected to an eye level viewfinder by a mirror and prism. So that u see exactly what the film will register.
While you are viewing the scene before taking the picture. Light passes freely through the lens. Its path towards the film is intercepted by a mirror that reflects the light upwards to a ground glass focusing screen at the top of camera body. This screen is 24 x 36 mm. the size of the picture frame as it will appear on the film. The distance from the lens to the screen via the mirror is exactly the same as the distance from the lens to the film. Looking into the eyepiece, you view the image on the screen through a pentaprism. A block of glass shaped to present the image upright and the correct way round. As you vary the focusing and framing of the image, you can see it changing in the viewfinder.
Virtually all SLR have a built in exposure meter coupled to the shutter speed an aperture. A display in the viewfinder indicates when exposure is correct as you change these controls or else the camera adjust the shutter and aperture settings by itself.
In some SLR the diaphragm, which it built into the lens. Is closed down to the value set on the aperture control during viewfinding. In an increasing number of cameras. However, the diaphragm stays fully open during viewfinding. So that the image is seen at maximum brightness, and closes down to the set aperture only when the button is pressed.
Until the moment when the button is pressed, the film is protected by the shutter blinds (either metal or cloth) in front of the film.
When you press the shutter release button on an SLR, a complex sequence of events is started. The modern SLR has evolved into a delicate and elaborate instrument that carries out this sequence as smoothly and silently as possible. The mirror swings up out of the light path, blocking off any light that may enter the camera through the eyepiece, and the image vanished from the viewfinder. At the same time the diaphragm closes down to the aperture that has been set.
Then the exposure begins. The shutter blinds move in such a way that a gap traverses the film. Allowing light to fall on the film (see page 18). When this has happened and the film is again covered by the light – tight shutter, the mirror springs back into place, the image reappears in the viewfinder and the film can be wound on for the next shot.
The image in an SLR viewfinder is large and bright an its farming is exactly that which will appear on the film. Not only the focusing of the subject but it's depth of field-the range of distances over which objects are in focus-can be seen and precisely controlled. Most important of all, if a different lens is used on the camera body the viewfinder will continue to present exactly what the film "sees". You can also see directly the effect of filters attached in front of the lens. The SLR has proved itself to be most versatile type of camera.
The non-reflex camera
Despite the attraction of the SLR, some photographers prefer non-reflex cameras. Some SLR are bulky and heavy, and even the best of them cannot be as smooth and quiet in operation as comparable non-reflex cameras. There is a danger of camera shake caused by the mirror movement. The complexity of mechanism means that there is more to go wrong mechanically. And some users are bothered by the loss of image when they take the shot, even though this is usually momentary.
A non-reflex camera is intrinsically simpler than an SLR and hence more reliable quieter. It can be very compact-the smallest in the 35mm format being smaller than the palm of the hand. The viewfinder can be very sophisticated, incorporating a rangefinder coupled to the focusing control and an exposure meter that views the scene through the taking lens, like exposure meter on an SLR.
But the great disadvantage of the non-reflex camera is that in all but the most expensive models, there is a fixed lens-it cannot be changed because that would need a corresponding change of viewfinder. Also the effects of lens filters cannot be directly viewed. Nevertheless, the compact and convenient viewfinder camera has it devotees.
There are sophisticated non-reflex cameras with interchangeable lenses for which the viewfinder framing alters automatically when a new lens it put on. The exposure meter's light-sensitive cell is usually mounted behind the lens and springs aside when the picture is taken. A built-in shutter protects the film while the lens is changed.
This tiny 35 mm camera shows the compactness that the non-reflex camera can achieve. The minox 35 GT is just under 4 inches long, 2 ½inches high, and weighs only 7 ounces. When the protective flap is closed to retract and cover the lens, camera is little more than an inch thick. There is a built-in exposure meter, and the camera sets the correct shutter speed once the aperture has been set on a ring around the lens.
The roll film SLR
Some single-lens reflex cameras are designed for 120 roll film, which offers a choice of frame sizes considerably larger than the 24 x 36mm of 35mm cassette film. Some of these cameras have interchangeable backs, one of each format. Frame sizes range from 45 x 60 mm through 60 x 60 and 60 x 70 to 60 x 90 mm. normally the camera is held at waist level. The ground glass focusing screen is viewed through a magnifier that can be folded down when the camera is being carried. The image is upright be reversed from left to right. Pentaprism attachments are available for most models so that the camera can be used at eye level.
The twin-lens reflex camera
Most of the advantages of the SLR are offered by the mechanically simpler and more reliable twin-lens reflex (TLR) camera. In this design you view the image not through the taking lens but through a second lens mounted above it. This lens can be simpler than the main lens. Its image, reserved from left to right, is formed on a focusing screen at the top of the camera body and is viewed through a magnifier. The two lenses move together as the image is focused. The image in viewfinder is not exactly identical to that to that seen by the taking lens, because of the difference in the positions of the two lenses. But it is only for very close subjects that this difference becomes important, and the viewing screen carries marking that indicate the true image area for close subjects. Lenses are not interchangeable on most models of TLR, since both the lenses would have to be changed together.
The technical camera
The greatest degree of control that a photographer can achieve is provided by the so-called technical camera, although only with a loss of operating speed and convenience. As used in the studio, the technical camera consists of a front and back panel, carrying the lens and film holder respectively, joined by lightproof folding bellows. The panels move independently along a steel "monorail" mounted on a tripod. During the setting up of shot the back panel carries a ground glass focusing screen on which the image appears upside down and reserved from left to right. When the shot is about to be taken the screen is slid out and replaced with a film holder containing and individual sheet of film. Any lens can be used in the front panel. Not only can the panels be slid backwards and forwards, they can be raised and lowered or twisted for various special purposed (see page 179).
Portable versions of the technical camera have the front panel sliding on a baseboard that folds out from the back panel. There is a ground glass focusing screen, but normally a supplementary viewfinder with a coupled rangefinder is used. The baseboard camera can take flat film or roll film.