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The Single Lens Reflex Machine.. How a Camera Works.. The Book of Photography

The Single Lens Reflex Machine

In the future, historians of the art of photography will conclude that the single lens reflex machine is the best machine produced in our time. This success is attributed, on the one hand, to technical developments and, on the other hand, to the wide (market) that photography represents today, because this machine actually has many advantages: lightness, compactness, ease of use, a variety of shooting methods, an internal zoom, a wide variety of interchangeable lenses, and a complete set of additional parts. The machine is completed by a well-crafted and inexpensive positive light (diapositive or positive slide) lamp. Finally, the improvements made to black and white films enable the images to be magnified several times without grain appearing on the image.

The image given by the lens - for the focus - is reflected by a movable mirror curved 450 on the focus glass on which this image is formed, i.e. the image on which it is focused is exactly the same as the image that will be recorded on the film when the button is pressed, in other words there is no angle of deviation or difference. There is a spring-operated mechanism that connects the mirror to the image-taking mechanism, i.e. the mirror evades and passes the light beam completely before the starting of the burning shutter. The method of focusing has been improved by a mechanism containing a pentagonal prism and a magnifying lens that gives an enlarged and straight image of the subject at which it is focused.

The main elements of a single-lens reflex machine are the focus and the burning shutter. All 24 x 36 mm reflex machines that use 35 mm film have a pentagonal prism, while some Single-lens reflexes that use larger films than the above-mentioned size are only fitted with this piece on request. The main difference between the various small-sized models lies in the interchangeable lens mounting: they can be fitted with a screw, a sheath or a male and female with a tightening ring. The built-in focus meter, the automatic pre-selection of the pupil aperture which gives a theoretical estimate of the depth of field obtained at the selected aperture, advanced calibration mechanisms, etc., are available in almost all models. Some machines, whether small or large, can receive an interchangeable back or a motor to advance the film.

Medium-sized single-lens reflex

Larger than a 35mm machine, it produces 4.5 x 6, 6 x 6 or 6 x 7 cm images on 120 or 220 film. The focus glass has lengths equal to those of a cliché and the focus is at eye or chest level. The lenses, focus lenses and magazines are often interchangeable.

35mm style

The 35mm single lens reflex accepts interchangeable lenses with their accessories (filters - sunscreens - bellows and zoom rings), motors, remote controls, flash, etc. Most devices offer boxes of varying degrees of perfection but can use the same lenses and accessories.

Interchangeable lenses

The machine is delivered with a regular focal length called (standard) but there are many types of lenses that meet all specific needs: telephoto lens, fisheye lens, wide angle lens, etc. Their focal length can start from 15 mm (maybe less) to 1000 mm (or more)

Wide angle lens

All lenses that cover and expose a field equal to or greater than 600 are called wide angle lenses. They are compact and light and their focal length starts from 35 mm to 15 mm for very wide angle lenses and expose a field of 180°.

Long focal length lens

It gives more magnification than a standard lens and these lenses range from 85 to 1000 mm. The most commonly used of these lenses is the 135 mm which exposes and covers a field of 18°. Its size and weight increase with increasing focal length.

A self-moving or manual pupil for examining the image at the actual aperture. Many lenses are equipped with a manual mechanism for pre-selection.

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Magnifier for expressing the image

A changeable focus bottle.

In some machines the manufacturer can change the focus bottle and others have a focus bottle that can be moved and changed by its user, for example the standard bottle can be replaced with a very smooth matte bottle for very precise expression.

Posometer under tension.

Film type announcement location

Colour latch

Rewinding film and opening the back

Flash socket. Synchronous nail with holder for extra parts. Synchronous hanger when using electronic flash without tape. On the other hand, the case contains FP and x synchronization sockets for the synchronization tape.

Lens latch

Screw mounting or by pillars The lenses are mounted in some machines by screw and their universal diameter is 2 mm, while in other machines the lenses are fixed in them by pillars of a specific type according to the type and brand of the case.

Interchangeable lens: In some sophisticated devices, the pentaprism lens (commonly used) can be replaced by a sports lens or a chest-level lens or a zoom lens.

Standard lens according to the types. Aperture from 50 to 58 mm (field angle from 47 to 43°) and an aperture of F / 1.8 | F / 3.5.

Additional rings. They overlap each other between the general and the body of the camera to allow taking unusual pictures (between 10 and 45 cm). Most of them carry the automatic pre-selection and the necessary functions of the liposome in the attic.