PhotoHistory

From: Complete Self-Instructing Library of Practical Photography
Volume I - Elementary Photography

The Camera How to Operate It

By J. B. Schriever, 1909

Lenses

The camera, whatever its type, is not complete without a lens. The simpler types of cameras are provided with the simpler forms of lenses, the simplest of all being the single, or Meniscus lens, which is generally fitted to box cameras and the cheapest folding cameras of the fixed focus type. The single, achromatic, or view lens, as it is sometimes styled, is limited in its scope. For instance, it is not capable of accurately reproducing lines such as the corners of buildings. It is not a fast lens, and its angle of vision is a narrow one.

Of greater general use is the Rapid Rectilinear lens which being made up of two or more lenses attached to each end of the lens barrel belongs to the doublet type of lenses. Most hand and film cameras are supplied with such lenses, which are capable of accurately rendering straight lines and give a more or less even definition over the plate for which they are adapted. The single set of lenses of a doublet can be used by itself as a view lens, and then gives an image of twice the dimensions of the doublet lens.

For a still further type of lens, which has all the advantages of the rectilinear just mentioned, and adds to these the further advantages of great speed, great brilliancy and fine definition, is the modern or anastigmat doublet. Such lenses are of various types, and when fitted to hand, view or reflex cameras enable the worker to do the very highest type of work. For certain forms of work, such as the photographing of buildings and interior views, where the worker is not able to recede far enough from the object to be photographed, a fourth type of lens is necessary. Such a lens is called the wide-angle lens, which is so constructed as to enable the worker to get near to his object and still get it all within the dimensions of his plate.

Shutters

To enable a picture to be made, some sort of a contrivance is necessary, by which the light can be admitted through the lens for a stated period of time. Such contrivances are called, in general, shutters, and are of varying types being placed in front of the lens, or between the lens, or behind the lens and in front of the plate, according to their type and the results they are called upon to produce. In box type cameras and the cheaper folding cameras which are fitted with single lenses only, a shutter that works in front of the lens is used, either the simple rotary shutter, such as we find on the box type of kodaks and cheap plate box cameras, or the single valve shutters, such as are usually fitted to cheaper folding cameras film or plate. Doublet lenses have the shutter fitted into the barrel midway between the two lens cells. These shutters, being either of the single valve, double valve, or automatic type, work either by pressure on a small external lever or by the pneumatic pressure of a rubber bulb or tube attached to an air valve on the shutter. The remaining type of shutter is that which is commonly fitted to reflex cameras, and consists of an opaque curtain which passes rapidly in front of, and very close to, the sensitive plate, admitting the light through an adjustable longitudinal slot in the curtain. Infinitesimal exposures can be obtained with this shutter, known as the focal plane shutter.

Operating the Shutter

The Rotary Shutter is automatic in action and always set. It is operated by pressure on a lever, which protrudes from the side of the box. To obtain an instantaneous exposure, one press on the lever will open and close the shutter simultaneously. By pulling out a small bar or lever projecting from the side of the camera the shutter can be used for time exposure. To obtain a time exposure two presses of the lever are required — one to open the shutter, admitting the light through the lens, and another to close the shutter, cutting off the light. The diaphragm openings are controlled by a lever in a similar manner to the time exposure.

Single Valve Shutters are provided with a dial and a pointer, the dial being marked T, B, I. When the pointer is turned to the letter T the shutter is then set for what is termed a time exposure; the lever or one squeeze of the pneumatic bulb will open the shutter, and a similar movement on the lever or bulb will close the shutter. If the pointer be turned to the letter B, the shutter is then set for what is termed a bulb exposure; that is, the shutter will remain open just so long as the lever is held down, or a pressure is exerted on the bulb. Releasing either will instantly close the shutter. The use of the bulb exposure is more particularly for photographing objects which are liable to move, and with which more than an instantaneous exposure is permissible. The I on the dial signifies instantaneous, and when the pointer is adjusted to this letter the shutter will work instantaneously when the lever or bulb operates it. The duration of the instantaneous exposure with these shutters is about equivalent to 1/33 of a second.

The Double Valve Shutters are similar in their work to the single valve shutter, but are more accurately adjusted and supplied with a greater range of movement. Usually the dial is provided with T and B markings, and from 1 second to 1/100 of a second. To obtain the various exposures the pointer is set to the letter or fraction of a second required. Typically this shutter is fitted with two levers, one used for setting the shutter, while the other is used to release it to make the exposure.

The double valve shutter is also fitted for a bulb and tube with which the exposure can be made instead of with the finger release. On the top of the shutter there is a small dial, containing the letters B and T; the dial is also marked in figures from 1 to 1/100, representing seconds and fractions of a second. When the dial, is turned so that the indicator is placed at T it means time exposure. To set the shutter pull down lever. After setting the shutter, one pressure of the bulb or pressing down on the lever or finger release opens the shutter and it remains open until the bulb or finger release is again pressed, when the shutter is closed.

Timed exposures

When the dial is placed at B the shutter will remain open as long as the hand presses the bulb or the finger holds down the finger release. It is advisable to use B, or the bulb, for all exposures ranging from one-half to two seconds, as it is more simple to operate. For all exposures requiring longer time, the T or time exposure should be used.

When instantaneous or quick exposures are required, then the dial should be set at 1/100, 1/50, or 1/25, which indicate fractions of a second. The proper one to use depends on the strength of light. In real bright light 1/100 is best, and in medium light 1/50 or 1/25. When set at 1/100, which is the quickest exposure that can be made with such a shutter, one pressure of the bulb or pressing down of the finger release will make an exposure 1/100 part of a second. When the dial is placed at 1/50, 1/25, 1/5, or 1/2, one pressure of the bulb or pressing down the finger release will give the indicated fraction of a second exposure.

To focus the camera turn the dial at T, set your shutter by pressing down the finger release, C, opposite the side from which your tube is attached; then, one pressure of the bulb will open the shutter and permit you to see the image on the focusing screen (ground-glass).

Automatic Shutters are made of the single valve and double valve type, and also without any visible valve, and are termed automatic for the reason that they are always ready for exposure without having to be “set,” as the older forms of single and double valve shutters have to be. The automatic shutter can be seen to have its advantages over the older forms, but at the same time greater care is necessary in seeing that the shutter is not opened inadvertently through a pressure of the bulb, which could not take place with the older shutter before it was set. The setting of the speed in this class of shutter is practically the same as for the older forms.

Diaphragms or Stops

An indispensable part of all between-the-lens shutters is the diaphragm or stop, which regulates the quantity of light passing through the shutter to the plate or film. The diaphragm or stop in a shutter is usually an opening which can be regulated from outside the lens barrel, making it larger or smaller in proportion to the amount of light it is desired to admit to the plate, and also in proportion to the sharpness of definition that is required on the plate.

Iris Diaphragm

Originally diaphragms were metal plates, each having an opening in the center, of different diameters, ranging in geometrical proportion to the focal length of the lenses to which they belong. They are known as Waterhouse stops, and are inserted in an opening in the lens barrel. The majority of lenses and shutters fitted to the common hand cameras now contain a device known as the Iris Diaphragm, whereby the opening may be decreased or increased in size by the single movement of the indicator. When this lever is turned to any of the figures on the plate at the bottom of the shutter it indicates the proportionate amount of light admitted. The smaller the aperture the greater will be the depth of focus of the lens.

Depth of Focus

By depth of focus is meant the power which a lens has of rendering a sharp image upon the ground-glass, of objects situated at varying distances. When using the lens at full opening, it is difficult to obtain at one and the same time a clear and sharp image on the ground-glass of both near and distant objects. To obtain this increased sharpness you must make use of the stops or diaphragms. This gives increased depth of focus.

Use of Diaphragms

The diaphragm markings are usually arranged at the lower part of the front of the shutter. By using the smaller opening, diaphragming down, or “stopping down,” as it is commonly termed, a portion of the rays are cut off and a much greater depth of focus secured; but in employing a smaller opening, cutting out the rays of light, the exposure necessary is greatly increased.

There are many defects in some of the cheaper grades of lenses, and, aside from giving a greater depth of focus, the use of a smaller stop corrects different aberrations or defects. The more important points to be remembered in using a diaphragm are these:

First, the larger the aperture the more roundness, atmosphere or effect of distance is obtained, the picture presenting a bolder appearance; but a more rapid exposure is required.

Second, the smaller the aperture the longer the exposure, the greater the depth of focus and the sharper the image, accompanied by a corresponding loss in relief. When focusing always have your lens wide open (full diaphragm). After obtaining the focus, stop down only enough to give clear detail in the picture.

To Focus the Camera

Whatever the type of shutter used, set it at the time exposure and open, using the largest stop or diaphragm. The light will then pass through the lens, permitting you to see the image on the focusing screen or ground-glass. By moving the lens support i.e., on folding cameras to and fro on the track, the image on the ground-glass can be brought to a focus, which means clear, sharp definition. With kodaks which are not provided with a ground-glass or focusing screen the focus is obtained by gaging the distance from the camera to the object being photographed, and setting the pointer on the lens support opposite that distance indicated on the focusing scale.

Regulating Different Openings According to Exposure

For snap-shot or instantaneous exposures employ the largest diaphragm or opening. In average view work such as open landscapes it is seldom necessary to stop down, i.e., reduce the aperture, smaller than the f/8, or its equivalent U.S. 4. (See following paragraph.) The smallest opening should be used only when extreme sharpness of the whole field is required. For example, when photographing an interior it will be necessary, in order to secure detail, to have objects close to the camera, in the middle distance, and those more remote, equally sharp.

The Size of the Stops are numbered in different ways, according to various systems. The two in most use are the “f” and the “U.S.” (Uniform System.) The f system refers to the relation of aperture to focal length; while the U.S. is a uniform series of markings based on the same principles. It may be as well to state here, that on shutters of American manufacture the Uniform System of numbering the stops is universally used, while the diaphragms on anastigmat lenses of foreign manufacture are marked according to the f system.

The corresponding values are given in the following series:

U.S. 1 2 4 8 16 32 64 128 256

f 4 5.6 8 11.3 16 22.6 32 45 64

The exposure with a certain stop is one-half of the next smaller and double that of the one next larger; i.e. if stop f/8 requires an exposure of one second, the next smaller, f/11.3, will need two seconds; while f/5.6, the next larger, will need but one-half second’s exposure, and f/4 one-fourth of a second. Or, in the U.S. numbers stop No. 4 requires one second, No. 8 will need two seconds, No. 2 one-half second, and No. 1 one-fourth of a second. The largest opening or the largest working aperture of the lens on the average hand camera is f/8 or U. S. 4. For the beginner, who is apt to become confused by the diaphragm numbers, it is well to remember that the large numbers indicate small openings, and that the smaller the opening the longer the exposure required.

Reversible Back

All modern high grade folding plate cameras are supplied with a reversible back. This is to enable the user to make either horizontal or vertical views by merely reversing the back attachment without changing the position of the camera. The back is held in place by means of firm clamps, which are easily released when desired. The ground-glass is attached to the frame of the reversible back, so it is always in correct position.