Photography
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Read about Photography in the Standard Cyclopedia of Horticulture
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For views outdoors of trees, plants, and the like, any view camera of the regulation or of the "folding" type will answer, although, as it is often desirable to obtain relatively large details of fruits or flowers or plants in situ, a bellows of more than the usual focal capacity or length is preferred. The modern "long-focus" cameras are suitable, and the size most used by horticulturists is that taking a plate 5 by 7 inches in dimensions. For such size a rectilinear lens with a focal length of 7 or 8 inches is advisable; and if one of the two lenses forming the combination is available as an objective of about double the focal length of the combination, and the camera is provided with a bellows which draws out several inches beyond the focal length of this single lens, much facility in operation is provided. Any of the modem high-class view lenses are suitable, and those of the anastigmatic type, which are not only rectilinear but also render views in a flat and correct perspective, are preferable. It need not be assumed, however, that the very highest-grade lens is essential, for in the hands of a thoughtful and reasonably skilful operator, an ordinary rectilinear lens, costing, for the size mentioned, but $15 or $20, will often do satisfactory work. Whatever lens is used, it should be fitted into a quick-working shutter, as outdoor exposures, with modern rapid plates, must be made in small fractions of a second. The shutter, it may be explained to the unacquainted reader, is merely a convenient device for opening and closing the lens to the light for the interval of time desired by the photographer. As there is frequent misconception of the work done by a lens, it may not be amiss to suggest to the inquiring horticultural photographer an investigation on his own account. The Photo-Miniature No. 140, "Lens Facts You Should Know," is a brief, clear, and concise statement of the principles, properties, and construction of lenses, which may be consulted to advantage. The focal length of any lens, in connection with the size of the plate upon which it is to be used, determines the Angle and amount of view included. The human eye is a lens of about 16 inches focal length, and to have a photograph render perspective as seen by the average eye, an objective of the same focal length is required. Thus, on a 5 by 7 plate, a lens of 8 inches focal length will include twice as much in the view, and show it in half" the size as seen by the eye. This forced perspective is sometimes desirable and sometimes unpleasant. If the 8-inch lens is composed of two elements on what is known as the symmetrical plan, the rear element may usually be used alone (by screwing out the front lens), and it will have approximately double the focus of the combination. This will give about the perspective seen by the human eye, and will need to be used in connection with a bellows of at least the same length or "draw" as the focal length of the lens. Some of the high-grade lenses are now made on what is termed the "convertible" plan, each of the two elements being of a different focal length. Thus a certain lens which as a whole is of 7 1/2 inches focus, includes one element of 12 inches focus and one element of 18 inches focus. Either of these single lenses, or the combination, may be used separately, so that from a given position three views, including proportions differing as 5, 8, and 12, may be made. To photograph an object in natural size, the double lens is preferable. If the lens is of 8 inches focus, it will give natural size when placed equidistant between the object and the ground-glass focusing-screen of the camera, at double its focal length. Thus the bellows would need to be drawn out so as to have 16 inches between the ground-glass and the lens, while the object to be photographed should be maintained in position 16 inches from the lens. A tripod, capable of adjustment as to height, and of sufficient rigidity to sustain the camera in a moderately high wind, is easily obtained. The cheaper forms are fairly efficient, but the photographer who has much traveling to do finds it preferable to obtain one of the more expensive and carefully fitted types, which fold into a smaller compass. For indoor work, including the making of photographs of fruits, flowers, or plants in large detail, a special form of camera-stand is very desirable. One arranged so that the camera may be maintained in an inclined or nearly vertical plane, while the object to be photographed rests on a plate-glass exposing-stand in front of the lens, gives great facility and ease of operation, and does away with many difficulties of illumination. A few experiment stations possess devices of this kind. A form which has been found exceedingly satisfactory in practice is described in an out-of-print number of The Photo-Miniature, "Photographing Flowers and Trees," and is here reprinted by permission in Figs. 2924 and 2925, showing the camera-stand both as arranged for horizontal and for vertical work. In operation with this device the flower, fruit, or plant to be photographed is laid upon or placed in front of the plate-glass stand, and the camera, fastened by its tripod screw upon a movable bed, is adjusted as a whole, or through its bellows, until the desired size and focus are secured. The background may be varied as desired by cardboards or cloths placed out of focus in relation to the plate-glass stand. The camera-stand is mounted on casters, so that it may be readily moved about to secure the most favorable lighting. Objects which can best be handled on a horizontal plane may be disposed somewhat as shown in Fig. 2924. For work of this sort a north side-light is found vastly preferable to the conventional sky-light. A greater mistake in the equipment of a studio for horticultural work could not be made than to provide the sky-light deemed essential by old-fashioned professional photographers, although now happily abandoned by the more progressive workers for a "single-slant" light, which gives far better results. There should be provided in the workroom of the horticultural photographer several good reflecting surfaces, so that the side of the object opposite the main source of light may be properly illuminated. All the apparatus above mentioned is applicable to color-photography by the Lumiere method, as hereinafter sketched; but motion-picture photography requires apparatus peculiar to itself. Under certain conditions, the use of the "flashlight" methods may be advantageous in horticultural photography; as, when an outdoor object must be obtained at night, or indoors where a flower may wilt under prolonged exposure. Flashlight processes depend upon the explosion or the rapid combustion of certain metals— as magnesium—which, either alone or in combination with oxygen-giving chemicals, produce a light of great brightness and high actinic power for an instant. Further information upon flashlight may be found in. The Photo-Miniature No. 135, "Flashlight Photography." The horticultural photographer also requires an outfit for developing and printing; but as this may be conventional, it is not deemed necessary to discuss it here. Photography Plates and color-values. As practically all horticultural photography has to do with the tints of growing things, the well-known color inaccuracy of the ordinary dry-plate is a serious disadvantage. The ordinary plate responds most actively to the rays at the blue end of the spectrum, and is very sluggish in taking an impression from green, yellow and red, the latter color, indeed, being rendered practically the same as black. Yellow, which in actual color-value is on a par with light blue, and sometimes to the eye seemingly more intense than white, is rendered by the ordinary plate as a dark color, as all operators who have photographed yellow roses, yellow apples, yellow plums, and the like, will have observed. Fortunately, there are available photographic plates, known as isochromatic or ortnochromatic plates, which, to a certain extent, correct these difficulties; and the skilful operator may, by the use of the proper plate and in some cases a suitable ray-filter, give approximately correct values to all the colors of the spectrum. For all ordinary horticultural uses, when blue and yellow are not found in the same subject, the commercial orthochromatic or isochromatic plates of the most rapid speed are satisfactory. These give to yellow its proper value, at the same time improving the rendering of the green foliage and slightly increasing the truth of representation in pink, lavender, and the lighter red shades. It is very much better, then, for the photographer who has to do with horticultural work to confine himself exclusively to these plates for all his work. If he has a subject including blue flowers, the especial activity of the blue rays, which otherwise would render the photographic impression as intense as if the object was white, can be restrained by a suitable ray-filter, which is applied in front of the lens. This ray-filter is either a glass cell filled with a 1 per cent solution of potassium bichromate, or a piece of plane optical glass covered with a suitably stained collodion film sealed with another optical glass and provided with a convenient mounting for slipping on the lens. (Such ray- filters may be commercially obtained at small cost, but ought to be known to be adequate for the particular plate to be used.) With this ray-filter and the plate before alluded to, the yellow is slightly over-valued, but the blue is given its proper relation. The beauty of outdoor photographs is vastly increased by the use of the plate and ray-filter mentioned, because a proper color- value is given to the sky, and the cloud-forms are preserved in all their attractiveness. If the subject is a heavily loaded peach tree, for example, the accentuation of the yellow, brought about by the use of the ray-filter, will give a needed slight exaggeration of color- value to the fruit, which, under treatment by an ordinary plate, will be almost indistinguishable from the mass of foliage. With the usual ray-filter the exposure required is practically trebled. In this Cyclopedia, advantage has been taken of orthochromatic plates in photographing many of the subjects. The carnations, Plate XXII. Vol. II, show a variety of shades properly rendered by the means indicated. The grapefruit. Plate L, Vol. III, is an example of the use of the ray-filter also to obtain the full color-value of the fruit. A difficulty known in photographic practice as halation must also be counteracted if the fine detail of subjects involving much light is to be preserved. Halation is caused by the reflection of brilliantly lighted objects from the back of the glass plate carrying the sensitive emulsion. Light possesses enormous velocity, and there is an almost inconceivably rapid play back and forth between the two surfaces of the glass plate, which is covered only on its face by the sensitive photographic emulsion. This results in a thickening of all the finer lines which should be rendered in the positive as white. It may be counteracted by "backing" the plate with a composition which will absorb all the rays of light that pass through the emulsion on the face; but in current practice a slightly less adequate and much more convenient prevention of halation is secured in the use of what are known as "double- coated" plates. A "slow" emulsion, first coated on the plate, is covered by a "fast" emulsion, with the effect of absorbing into the under-coating, in exposure, the overplus of light. These plates, incidentally, also give greater latitude of exposure, and their use. is recommended, with the provision that both coatings should by all means be orthochromatic. Even with the aid of the isochromatic plate and the ray-filter, the photography of shades of red is difficult, because of the lack of actinic or chemical quality in the red rays of the spectrum. In practice it is found necessary to give a very much prolonged exposure to objects containing red, and then to restrain the over-exposure upon development by means of a suitably compounded developing solution. Photography Lantern-slides. A lantern-slide is a positive on glass, and therefore is made from a negative. It is made preferably on a special plate, much slower than the regular photographic dry-plate, because coated with silver chloride rather than a stiver bromide emulsion. The slide is usually faced with a paper mask, so as to include only the desired portions of the picture, and protected by a cover glass. Negatives of any size may be used if a suitable arrangement is provided for reduction. This can readily be arranged by an adaptation of the camera- stand illustrated in Fig. 2924. A pair of light bars is added, running from the top of the plate-glass frame to a support at the other end of the stand, and a piece of heavy muslin or light canvas thrown over this serves to exclude the excess of light. A ground-glass frame is added back of the plate-glass, which latter is removed to give place to a turn-table arrangement, made to take and hold negatives of various sizes. In practice, the ground-glass end is turned toward the strong light, the negative to be used is adjusted in the turn-table, and the image focused in the camera as usual. The 5 by 7 size largely used by horticulturists is in just the right proportion for the ordinary lantern-plate of American practice, which is 3 1/4 by 4 inches. Slides may also be made by contact, if the negative to be used is of suitable size. The familiar 4 by 5, 3 1/2 by 3 1/2, and 3 1/4 by 4 1/4 hand-camera films are often so used, being placed in contact with a lantern-plate in an ordinary printing-frame, and given a short exposure to an artificial light. Such slides are seldom of good quality. If it is required to make lantern-elides from diagrams, engravings or any positive material, a negative is first prepared, for making which the vertical position of the camera-stand (Fig. 2925) is very convenient. For many diagrams and for most "reading slides," there is much advantage in making the slide directly without the intervention of a negative, with the result that the letters or lines are shown as clear glass. The audience sees only the message or object, the background being dark; and the excessive light reflection, tending to tire the eyes, is avoided. In making lantern-slides, it is important to learn the proper exposure, for errors in exposure cannot be corrected in development to any great extent. The careful worker will expose several plates upon the same subject, give all the same development, and act upon the experience thus gained. The standard all too often accepted by those who use lantern-slides is unfortunately low. Manufacturers competing wholly on the lowest price basis have accustomed even thoughtful persons to think their productions adequate, instead of which they are unfortunate, because they belie rather than reproduce the object to be shown. Lanterns for projecting these slides are now simple, convenient, and cheap. One form, available wherever access may be had to an electric-light socket, can be carried in a small case and set up for use in less than ten minutes. It perfectly projects an image up to 6 or 8 feet in diameter, and is without complications. Built of aluminum, it is solid and durable, and its cost is but one-fourth that of former apparatus. Colored lantern-slides. The value of a good lantern-slide is increased more than tenfold if the slide is so colored as to show upon the screen the object or scene in natural hues. It is not difficult, with suitable knowledge and sufficient practice, so to tint the lantern-slide as to accomplish this object, and there are a number of notably successful colorists whose work has given information and pleasure to thousands. In practice, if a lantern-slide is to be colored, it is usually mode slightly less dense or "contrasty" than if it is to be shown without color. A photographer's retouching stand, which excludes light from the eyes of the worker and reflects light through the ground- glass and also through the slide to be colored, is needed. Coloring is effected by means of the use of dyes and stains of various characters, usually obtainable in the market. The color is applied by the use of brushes of varying sizes. The capable worker constantly compares the result of his efforts, either with standard slides of high quality or through projection upon a screen by means of a small lantern. One reason why colored lantern-slides are so much more effective than those uncolored is in their exclusion of excessive light, which tends to dazzle and weary the eyes of the spectator, as previously suggested. Thus, a sky is blue and agreeable rather than white and dazzling. Transparent colors must be exclusively employed, inasmuch as the effect to be obtained on the screen through projection is wholly that of transmitted light, and not by reflection. The use of lantern-slides in general and of colored slides in particular for educational purposes has been greatly fostered by the action of several states in establishing departments of visual instruction, in which are grouped collections of carefully made lantern-slides upon various subjects, frequently available to residents of the particular states without other charge than transportation and a responsibility for damage. Pennsylvania, New York, Washington, Illinois, and Kansas are known to maintain such departments. Motion-picture photography. Reference has been made to the recent development of motion-picture photography. Motion-pictures are at present being viewed by many millions of persons daily in the various centers of population in the United States, but as yet little organized effort has been put forth for preparing motion-pictures primarily for educational purposes. Through the federal government, and in the Department of the Interior, the national parks are brought into notice by means of motion-picture films; and it is probable that a motion- picture outfit, both for the making of the exposures and for the proper display of the result, will shortly become an essential factor in connection with any modern educational institution. Particularly in reference to horticulture is it probable that the motion- picture will show to advantage orchard and planting operations and the growing of great crops (as before mentioned in connection with asparagus, for example), and similarly will teach quickly and entertainingly many things now less adequately presented. Photography in natural colors. Many investigators have worked on this problem, but without what might be called reasonable and available success, until, in 1907, the Lumiere brothers, acute opticians and plate manufacturers at Lyons, France, painstakingly developed what is known as the auto- chrome process. This process uses the known but unappreciated fact that color is not an inherent property of matter, but a sensation of the eye relating wholly to the character of light reflected from any object. Exceedingly minute particles of nearly transparent starch, colored to three primary hues, are intermingled and spread in a single layer over the surface of a glass plate, and upon this layer there is coated a sensitive and so-called panchromatic photographic emulsion. These minute starch particles, averaging about 5,000,- 000 to the square inch, serve when the prepared plate is exposed glass side to the object (contrary to the usual practice) to separate or screen out the reflections from the object transmitting certain intensities relating to the colors then expressed in that particular light. Thus, from a red rose with green leaves, light is reflected through these dots to the effect that the underlying photographic emulsion is suitably affected for the purpose in mind. After exposure there occurs a process of development and re-development which removes most of the photographic emulsion save such as marks out the delineation of the object as depicted by the lens, and as will serve to obscure the colors not wanted. Under favorable conditions, the effect is an actual photograph in color upon a glass plate or transparency, which must be viewed as such by transmitted light suitably reflected from a white cloud or a white surface. If the light used in reflection has a differing spectrum from that used in the making of the view, the colors will not be seen as they were when the photograph was taken. As yet no means have been devised for adequately duplicating these transparencies on glass, which, therefore, while very beautiful when properly made and viewed, serve rather as color memoranda or records than for the reproductive purpose conceived of an ordinary photograph. In this book use has been made of the autochrome for obtaining the color records upon which the various color plates have been produced. For example, Plate VIII, Vol. I, showing the York Imperial apple, is a successful reproduction of an autochrome, as also is Plate XX, showing hardy bulbs in full color, and Plate XXV, celery, showing current commercial practice in exact color. These autochromes are relatively expensive to make, but require only a special ray-filter in addition to the ordinary camera equipment. With autochrome plates the careful worker is able to obtain many important and delightful records. Inasmuch as the autochrome is viewed with success only by transmitted light, it early occurred to those working in this method to propose the autochrome as a means of obtaining a perfectly colored lantern-slide. Several collections have been made which show in an exceedingly beautiful manner great scenery, portraits, and the like, but the disadvantages encountered are to the effect that inasmuch as the autochrome is much less transparent than the average lantern-slide, it cannot be shown with success in connection either with an uncolored or a colored lantern-slide. If autochrpme lantern-slides are grouped together and shown in a relatively small image with a very intense light (preferably that of the electric arc only), the result is excellent. Other methods said to accomplish color photography spring up from time to time. So far, however, not one of them nas been found to be of a permanently valuable and desirable character, or in any sense equal to the autochrome, which in itself is rather inadequate. The use of photography in relation to horticultural education and merchandising is merely in its infancy. It is probable that greatly improved methods of reproduction will permit of the more extensive and more effective use of photographs, and it seems certain that the moving-picture will assume a much greater importance in educational, philanthropic, and commerical practice. Acquaintance with photography is, therefore, likely to prove of increasing value to the horticulturist, J. Horace McFabland. CH
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References
- Standard Cyclopedia of Horticulture, by L. H. Bailey, MacMillan Co., 1963
External links
- w:Photography. Some of the material on this page may be from Wikipedia, under the Creative Commons license.
- Photography QR Code (Size 50, 100, 200, 500)