Photography self taught

He who builds a house, manufactures an automobile, works the farm, or produces a picture, must have certain materials and tools to work with. In the case of photography the tools consist of the camera and its accessories, the sensitive films or plates, chemicals and other supplies.

TYPES OF CAMERAS

Box Cameras, when reduced to their simplest form, consist of a light tight box with a lens at one end and a place for the sensitive film at the other. Such cameras are usually fitted with a fixed focus single (meniscus acromatic) lens, one or two ground glass view finders, and a simple type of shutter. Also, there may be a system of two or three “stops” for regulating the amount of light admitted by the lens.

A camera of this type is well suited for children and for the beginner. There is nothing much to get out of order, the camera is ready on the instant for whatever photographic subject may turn up, and the pictures obtained compare very favorably with those produced by the most expensive instruments. However, such cameras have their limitations. Snapshot exposures are only possible in good light when the sun is shining on the subject; objects nearer than about 10 feet cannot be photographed unless an auxiliary lens is used over the regular lens, and the camera is not so convenient for carrying as a folding type. The Brownie is one of the best known of box cameras.

Folding cameras, such as the Kodaks, are preferred by the great majority of workers. These range from the very small folding models of vest pocket size taking pictures 1⅝ × 2½ inches, through the 2¼ × 3¼, 2½ × 4½, 2⅞ × 4⅞, up to the 3¼ × 5½, which is one of the most popular sizes.

Cameras of this type ordinarily have rapid lenses and many are fitted with the highest type of anastigmat lenses. Brilliant view finders are usually furnished as the image is much more clearly seen than in a ground glass finder. They are ordinarily fitted with shutters which in addition to time and bulb action may work at automatic speeds from one second to perhaps ¹/₂₀₀. This makes it possible to get snapshots of subjects under conditions that would be out of the question with the box cameras with their slower lenses and shutters. Some of these cameras are provided with an autographic feature so that data can be made on the film at the time of the exposure. Some are fitted with combination backs so that accurate focusing may be done on the ground glass on the back. Most styles use roll film although some are fitted to take film packs and cut film.

Reflecting cameras fitted with focal plane shutter, are the type preferred by many advanced workers. A mirror reflects the image onto a ground glass, full size and right side up where it is focused and remains visible in a hood until the very instant of exposure, and thus it takes all the guesswork out of composition, lighting and focusing. Some focal plane shutters work as slow as ⅕ second. Such an exposure is very useful for home portraits indoors where the light is good. Focal plane shutters also permit of extremely rapid exposures. Cameras of this type are used when photographing automobile races, athletic events, etc. Naturally a reflecting camera is somewhat larger and heavier than an ordinary folding camera.

There are also many scientific, commercial and special purpose cameras, among which might be mentioned stereoscopic, telephoto, photomicrographic, enlarging, copying and reducing, lantern slide, identification, finger print, cirkut, panoramic, studio, view and motion picture cameras.

Practically all amateur work today is made with small film cameras. In many of the amateur photographic exhibitions large pictures will be seen but in most cases the foundation of these pictures was a small film negative. In selecting a camera it is well worth while to consider the fact that any camera, even the cheapest will make fair pictures under favorable conditions. It is only when convenience in regard to compactness and ease of operation along with the ability to fully expose and make microscopically sharp pictures under unfavorable conditions are desired, that the more complicated and expensive models are of superior advantage.

LENSES⁠[2]

In order properly to understand the purpose and use of the lens it is necessary to know something about the nature of light. Light ordinarily travels in a straight line but when a beam falls on a polished surface such as a looking glass it is reflected back in the same way that a rubber ball striking the ground rebounds. It is this reflected light from objects, that reaching our eyes enables us to see them, and reaching the lens of the camera enables us to photograph them.

As in the case of sound where low pitched notes are caused by a small number of vibrations per second and high pitched ones by a great number so in the case of light the red is produced by long wave lengths and violet by short ones. Between these are all the other colors from red to violet—orange, yellow, green, blue. There are wave lengths shorter than violet called ultra-violet, which are not visible but are very active in affecting a photographic emulsion. White light is made up by all colors.

Refraction is another property of light which very directly concerns our discussion of lenses. When a stick is placed in water at an angle, it appears to be bent at the surface. The explanation of this is that in a dense medium, light travels slower than in air. When the beams strike the surface one part reaches the surface and is slowed up while the other part is still in the air and traveling faster, thus causing a change in direction. The same thing taking place in glass explains the action of light in passing through the lens.

PINHOLE LENS. The simplest lens which we could use would be a small hole. If we take a sheet of cardboard and make a hole in it with a pin and then in a darkened room, hold the cardboard between a sheet of white paper and an electric lamp we shall see on the paper an image of the lamp’s filament. The same principle is applied to the making of pinhole photographs. A very fine smooth hole is made in a piece of thin brass or tin-foil and this is used in place of the lens. The diagram (Figure 1) shows how the image is formed by the use of the pinhole.

Remarkably good pictures can be made with nothing but a pinhole for a lens. No object is perfectly sharp but all are equally sharp and the result may be very fine pictorially. However, the exposure is very long, taking from a few seconds up to several minutes with the object in good bright sunlight even when a very fast film is being used. As the pinhole is made larger so as to admit more light, then the image will become more and more indistinct until no picture is formed at all.

FORMATION OF AN IMAGE BY A LENS. When a ray of light passes through a prism it is bent as it enters the glass and again as it leaves it. The lens works very much the same as two prisms.

The lens is used in the front of the camera for the purpose of so directing the rays of light that they will form an image of the object being photographed on the sensitive film or plate in the back of the camera. Figure 3 shows how the image is formed by the lens. It will be noticed that parallel rays of light are bent so as to go through F (the principal focus) and that rays passing through the center of the lens do not change in direction. This determines how far away the image will be from the lens. If the subject being photographed is 100 feet from the camera, the image will be formed a fraction of an inch closer to the lens than will be the image of an object only 10 feet away. This is shown by dotted lines in the diagram.

Focusing is the bringing of the lens to the proper distance from the film so that the image will be sharp, and as explained this is changed according to how far away the object is which is being photographed. This distance from the optical center of the lens to the focal plane or position of the films when focused on a distant object is termed focal length. When choosing a camera and lens for ordinary usage it is well to select one having a lens of a focal length at least equal to the diagonal of the negative. A short focal length lens gives a small image. For this reason the worker is inclined to approach close to the subject in order to get a larger image. In such a case any portion of the subject such as a foot or hand of the person projecting a little toward the camera, will appear much too large in proportion to the remainder of the subject. This is often noticeable in amateur pictures. For instance, the focal length of a lens on a post card size camera should be from 6½ to 7 inches.

KINDS OF LENSES. The meniscus lens is the simplest type, being made from a single piece of glass. Such lenses are used only on small fixed focus cameras. When a beam of light is passed through a prism it will be noticed that a band of color is formed. This is because the longer wave lengths such as the red colors are bent less than the shorter ones such as the violet. A meniscus lens will not focus the various colors in the same plane and therefore is used only on the very cheapest cameras.

A meniscus achromatic lens is more fully corrected, being made from two kinds of glass, flint and crown, and overcomes the difficulty just mentioned. Such lenses are used on most of the box cameras and the less expensive folding models. These lenses are made to be used only with rather small openings and so the user is limited to making a snapshot exposure in good bright sunlight. A lens such as this is very fine for landscape work or portraiture but if the subject is a building or other object containing straight lines, the lines will appear slightly curved if they come near the edge of the picture. If the stop opening is in front of the lens the lines will curve outward, but if behind it then they will curve inward.

Double lenses overcome this defect by combining two single lenses, one in front and one in back of the stop, so as to get straight lines to photograph as such, clear to the very edge of the picture. These lenses can be used at much larger stop openings in proportion to focal length than the meniscus achromatic or single lenses, and hence the name for the old type of double lens—“rapid rectilinear.” These older double lenses still have one defect known as astigmatism or the inability to photograph both vertical and horizontal lines sharply to the very edge of the picture.

About 30 years ago, Professor Abbe and Otto Schott working together at Jena, found how to produce new kinds of optical glass from which lenses could be made that would give flat field images with the blue and yellow rays at the same focus. By the use of these new glasses the opticians have been able to make lenses that give sharp images and a flat field to the very edge of the picture. These lenses are called anastigmat. Better defining power, however, can only be obtained by the most careful and skilled work when making the lens, this work being of a far higher quality than that applied on the older types of lenses, which accounts for the higher cost of anastigmats. They can be used with larger stop openings and thus it is possible to make snapshots on days when the sun is not shining and also to get slow snapshot exposures near a window if the light is good.

The “Kodar” lens is a recent development intermediate in type between the old “rapid rectilinear” and the anastigmat. It has many of the practical advantages of the latter though it is an inexpensive type of lens.

There are several types of lenses which are used for special purposes. Two of the most common are wide angle lenses and telephoto lenses. Wide angle lenses have a very short focal length for the size of the film or plate covered and are especially useful for photographing in confined positions, such as in a room where it is desired to include the greater portion of it. They are also rather necessary when trying to photograph buildings on the opposite side of a rather narrow street. The perspective is rather poor when working up close, as nearby objects appear too large in proportion to those more distant. The room looks much larger than it really is. Wide angle lenses must always be used with a smaller stop opening than those of ordinary focal length. For example, the Bausch & Lomb Medium Wide Angle Protar Lens Series IV has a maximum speed of f.12.5. The extreme wide angle Protar lens made by the same firm has its largest stop opening at f.18. The Goerz Hypergon lens has only a maximum opening of f.22, but this lens embraces an extremely wide angle of 135 degrees. The lens on the average hand camera includes an angle of perhaps 42 to 49 degrees.

Telephoto lenses on the other hand are most useful for photographing objects that are so far away as to appear too small with a normal lens. Not only are they useful for photographing animals, birds, and other wild life but are useful for taking pictures of persons or buildings that are not usually accessible. As the light reflected from the subject must cover a larger proportion of sensitive film, it naturally follows that the exposure would be longer than when no telephoto lens was used. A steady tripod must be used as the least vibration will spoil the picture. A longer bellows draw is generally necessary although some of the new fixed magnification telephoto lenses do not require a long bellows extension for the equivalent focal length.

Soft focus lenses, an example of which is the Wollensak Verito f.4 lens, produce an image which is very pleasing for certain types of pictorial and portrait work.

STOPS AND SHUTTERS

When using a camera, it is very necessary to know something about stops or diaphragm openings.

A very instructive experiment for the beginner, if he has a camera with a ground glass focusing screen, is to set it up in front of some well illuminated object and focus it on the ground glass screen by moving the lens nearer or further from the ground glass. A coat or other dark cloth should be thrown over the head of the operator and back of the camera to exclude the light. When the shutter is set so as to remain open and the largest stop opening is used it will be noticed that there is a brilliant image of the subject on the ground glass but that it is upside down. If the picture being examined is a landscape or other subject containing objects at different distances, it will also be noticed that those at a certain distance away will be sharply defined whereas others nearer and further away are somewhat diffused or blurred. In other words, they are out of focus.

If the size of the stop opening in front of the lens is decreased, it will be noticed that the image of objects nearer and farther than the one focused on becomes sharper, and that the image is not as bright as before. Thus we see that the two principal functions of the stop are to increase or decrease the depth of focus and to regulate the amount of light admitted to the sensitive film. This last function makes it an important factor in exposure. In the case of portraits it is usually better to have only the subject sharp for if the background were also sharp it would detract from the interest of the subject. For landscapes it is more necessary to have the entire picture sharp.

The amount of light reaching a given portion of the sensitive film depends not only on the size of the stop opening but on the distance of the lens from the film. With longer focal length lenses the distance is greater and therefore the light spreads over a larger area. Thus it is less concentrated, and so the exposure needs to be longer with the same actual size stop opening. The diaphragm or stop opening is always referred to in terms of its proportion to the focal length. In one system the stop is expressed simply as a fraction of the focal length. Thus, f.8 means that the diameter of the aperture or opening is ⅛ of the focal length. For example, if the lens opening or stop is ½ inch in diameter and the focal length is four inches, then the stop is f.8. Again, if the focal length is 8 inches and the stop opening is one inch the ratio would be the same, and the stop would be marked f.8. In the latter case four times as much light would have been admitted, yet it would have had to cover four times as much space thus giving equivalent illumination to the film. The comparative exposure of two stops varies with the square of their f. values, the larger numbered one being the slower and requiring the longer exposure. In the U. S. (Universal System), the stops are so marked that each succeeding smaller one requires twice the exposure of the next larger.

The following table gives a comparison of the two systems:

Most of the rapid rectilinear lenses have U. S. numbers. Anastigmat lenses usually have f. markings. The single lenses are more often marked with three or four numbers, 1, 2, 3 and 4, of which each succeeding larger numbered stop usually admits about half as much light as the next smaller and therefore requires approximately twice the exposure.

The shutter is a mechanical device for controlling the length of the exposure. One of the simplest forms is shown in the following diagram:

This form is known as a rotary shutter and may give snapshot exposures of approximately ¹/₂₅ of a second. An instantaneous exposure is made by pushing lever “C” across in one direction only. Ordinarily the largest of the three stop openings (controlled by slide “B”) is used for snapshots in good light, the middle one for snapshot exposures of very distant objects and for time exposures of interiors. The small one is more often used for time exposures outdoors. To make a time exposure slide “A” is pulled up and then when lever “C” is pushed across in one direction the shutter will open and remain open until lever “C” is pushed across in the opposite direction. Figure 5 illustrates one of the more comprehensive types of shutters. The size of the stop opening is controlled by moving “B” to the proper f. value.

FILMS AND PLATES

Photography begins with the chemical action of light on compounds of silver, particularly those of chlorine and bromine. This action is familiar to anyone who has added a solution of silver nitrate to a sodium chloride solution and watched the resulting precipitate of silver chloride darken after a short exposure to sunlight. Briefly, films consist of a base or support of either glass or transparent cellulose on which is coated an emulsion which holds in suspension some sensitive silver salts. Silver bromide is the principal sensitive material in films and plates. This, together with the gelatin which is added to keep it from settling, makes up the emulsion. The different degrees of sensitiveness are obtained by varying the amount and duration of heat to which the emulsions are subjected during manufacture. Other substances may be added which also affect its sensitiveness.

The silver bromide or other compound in the emulsion is so sensitive to light that an exposure in the camera for but a very small fraction of a second under good lighting conditions, is sufficient to produce a developable image. The emulsion is composed of innumerable grains, perhaps from 10 to 30 billion per square inch, lying several deep. The number acted on during exposure depends on the intensity of the light and the duration of its access to the film. The light action is not visible after exposure but every grain that was at all affected during exposure can be developed. This is explained later in Chapters III and IV. It naturally follows that if the sensitive film is exposed to light at any time other than when the picture is being made, for even the smallest fraction of a second before being developed, it will be completely fogged as all of the grains of silver bromide will be affected and when developed will be completely dark.

In addition to speed another characteristic of modern films and plates is latitude. This means that the exposure can be varied considerably without appreciably affecting the final picture. Thus, if the least correct exposure was ¹/₁₀₀ sec. this could perhaps be increased to ¹/₂₅, or four times as much, without affecting the final result except that the negative would be denser and require a longer time in printing.

Films or plates with very slow emulsions are more often used for copying and other work where it is desired to have considerable contrast and where speed is no object. The most rapid emulsions are necessary where extremely short exposures under ideal lighting conditions must be given, as for athletic events, and for slow snapshot exposures in poor light.

Ordinary plates and films are sensitive to the shorter wave lengths of light such as the ultra-violet, the violet and the blue, but little if any to the yellow and red. For this reason a blue flower or similar subjects will photograph so as to appear almost white, whereas a yellow or red one will appear nearly dark as the light reflected will not affect the film to any extent.

To counteract this some plates and most films are made somewhat color sensitive or orthochromatic by the incorporation in the emulsion of certain dyes which makes it less sensitive to blue light and more to the yellow-green rays.

For the exact rendering of reds and other colors, plates and films are sometimes still more fully corrected and these are termed panchromatic. While they are sensitive to all colors, yet they are somewhat more sensitive to the blues than the reds, and therefore a filter is often used.

The filter, which may be a piece of colored gelatin between two pieces of glass, is placed over the lens when photographing certain colored objects, and its function is to absorb or hold back the blue rays or certain other ones as desired. This will give time for the yellows and reds to affect the film and thus a denser deposit of silver will be obtained which will result in that part of the print being lighter. As the filter holds back some of the most actinic light, it is evident that the exposure will have to be longer than when no filter is used. The length of the exposure will depend upon the type of sensitive emulsion being used and the kind of filter. A variety of filters can be obtained which will absorb different colors and thus it is possible to have any given color photograph lighter or darker if desired. For full correction so that all colors will photograph to appear relatively as dark as they should, it has been found that Eastman Commercial Panchromatic Film and a Wratten K-3 filter will produce the desired result.⁠[3]

PRINTING PAPERS

Printing papers are sensitive in the same way as films or plates except that the emulsion is slower, and is coated on a paper base instead of glass or cellulose. The more rapid enlarging papers have a slow bromide emulsion while ordinary contact developing printing papers are usually silver chloride. The various contrasts and surfaces will be discussed in the chapter on printing.