Light display

“ There is a disc of cut glass in decorative designs, covering one hundred and forty-four electric lights in the form of a star, which is twenty-one inches from point to point, the centre being of pure white light, and each ray under prisms which reflect the rainbow tints. ”

“ When the sun failed to shine, or was not convenient, I practiced looking at a large incandescent electric light, and very soon the artificial lights troubled me no more than the stars which twinkle in the heavens at night ”

“ Two electric globes are made to cast the strongest possible light on the picture card set between them and in front of which a lens is placed to project the view on the screen, the whole being enclosed in a light-tight box. ”

“ Lighting.—Lighting our rooms is a matter of much importance. A student lamp, or shaded incandescent light, should be used for reading. Shades must be provided so that the eyes are protected from direct light. ”

“ If you want a really brilliant, clear, white light, you must trim the lamp yourself. A small piece of pale blue or neutral-tint glass interposed between the lamp and the microscope has a wonderful effect in diminishing the yellow hue which belongs more or less to all artificial lights which are produced by the combustion of oil or fat. We have no doubt but that in a few years we shall be rid of the clumsy and dirty machines that we call lamps, and have substituted for them the pure brilliancy of the electric light. ”

“ An object is now placed behind the screen, upon which the light of a strong lamp is thrown from a point above the mirror, and is received by the mirror and reflected to the center of the arched cavity in the screen, where it will appear to the spectator. Care should be taken to place the image in an inverted position, and the light, which must be very powerful, should be so placed that none of it may reach the opening. ”

“ For lack of them in streets and squares we may sometimes observe half the rays from a lamp taking their way to the sky where they do no good. In shop windows ribbed reflectors throw full illumination on the wares displayed, while the sources of light are out of view. ”

“ In dealing with lighting in the home the householder should concentrate his attention upon lighting effects. Unfortunately, he is not taught to do so, for everywhere he turns for help he finds the discussion directed toward fixtures and lamps instead of toward lighting effects. However, these are merely links in the chain from the meter to the eye. Lamps are of interest from the standpoint of quantity and quality of light, and fixtures are of importance chiefly as distributers of light. ”

“ An attractive design for a lamp-screen is shown in Fig. 1 A. When completed and backed with some pretty material it will be found a useful little affair to hang against the shade of a lamp to shield one’s eyes from the direct rays of a bright light.
To begin with, form a square of six inches, and at the top where the ends meet make a lap-joint by allowing one end to project over the other; then bind them together with some very fine wire—about the size that florists use. ”

“ In the arrangement with artificial light the illumination of the object to be taken is effected as a rule with a source of light which can approximately replace daylight, and which also remains as constant as possible, and the electric light is at present the best. ”

“ It is far easier to work with illuminated lines; and it is important to be able to control their brightness. I produce these lines by means of a vertical transparency, set in an adjustable frame, connected with A, and having a gas-light behind it. Below the eye-hole e, through which I view the glass-screen g, is a thin piece of glass set at an angle of 45°, which reflects the fiducial lines and gives them the appearance of lying on the screen, the frame being so adjusted that the distance from the thin piece of glass to the transparency and to the glass-screen g is the same. ”

“ This law does good service in autotypic work.
As we have seen, the rays of light must pass through the screen during exposure. This screen consists of equally thick opaque black and transparent white lines. Where the light acts with full intensity it will be more diffracted over the black lines. It makes the lines of the screen broader on the negative, and will, therefore, have more covered places, which in the after printing of the prints cannot be penetrated by the light, and thus represent the light places in the print covered with fine dots. ”

“ The screen screws are worked so as to gradually cut off the light, and the observer notes the appearance of the mirror surface. If the curves are perfect and spherical, the transition from complete illumination to darkness will be abrupt, and no part of the mirror will remain illuminated after the rest. ”

“ The one great drawback to their use, is, that they must be observed through glasses which are especially adapted to this purpose. Here in this inner world where it is never absolutely dark we cannot take the full advantage of these light signals, without the use of external appliances. ”

“ From recent experiments I am fully convinced that the lamp light, such as I have described, is capable of producing satisfaction, work with very much higher powers, and shall hope, at no distant day, to show prints made from magnification of not less than two thousand diameters, that will be satisfactory in all respects. ”

“ The powerful electric light, usually an arc light, which is placed in a metal box a few inches behind the rest of the projector, directs its rays through the glass condensers, thence through the film, and thence through the lens, which throws the image upon the white screen or curtain. ”

“ The mirrors are set in frames. In a panel behind the latter there is an aperture closed by a shutter. As the glass is transparent there may be seen through it, when the shutter is open, everything that is on the other side, so it occurred to the inventors to utilize this transparency by placing an image or photograph between the panel and the glass. On exposing the mirror to the light to look at one’s self in the ordinary way, if the shutter is open, the human head will disappear and may be replaced by the photographic [87] portrait or a horned devil, which is placed behind the mirror. ”

“ It can also be shown to a few persons at a time by means of the flame of a paraffin lamp twenty feet away, or even by the light of an ordinary candle a couple of feet away. In the case of these weaker sources of light the mirror must be held close to the white screen or card upon which the image is to be received. ”

“ The shutters that open the least will be those that are operated upon by the shadows of the picture. Inasmuch as a picture thrown on a screen from a source of light is wholly made up of lights and shadows, the theory is that this apparatus perfectly constructed would transmit any picture to a distance, through telegraph-wires. ”

“ High potential systems should be used only on the outside.
[269]
Illumination. Illumination.—Illumination is more an art than a science and the rules that can be given have only a very general application. The best practice, where really good illumination is desired, is to install a large number of circuits in proportion to the number of lights, so that lamps of large candle power may be used wherever desirable. The quantity of light needed in theaters varies greatly with the color of decorations and with their condition. Dust accumulates rapidly in theaters and may absorb half of the light. ”

“ From the footlights with their red and white and blue and vari-tinted bulbs, to the borders that light the scenery from above, the bunch-lights that shed required lights through windows, the grate-logs, the lamps and chandeliers that light the mimic rooms themselves, and the spot-light operated by the man in the haven of the gallery gods out front, all are under the direction of the electrician who sits up in his little gallery and makes the moonlight suddenly give place to blazing sunlight on a cue. ”

“ The Magic, or, more properly, the Projecting lantern, is an optical instrument, consisting of a case of wood or metal, enclosing a lamp or other illuminating agent, the light of which being gathered and condensed by a suitable condensing lens, and directed upon a small transparent picture, so powerfully illuminates it that its image, brilliantly lighted and greatly magnified, may be projected upon a distant screen by means of an objective—a combination of lenses in a tube—similar or identical in construction with a photographic portrait lens. ”

“ If the light of an electric lamp be caused to form a clear sunlike disk upon a white screen, the gradual change of this light by augmented precipitation into deep glowing red, resembling the colour of the sun when seen through fine London smoke, is exceedingly striking. ”

“ In fact, it answers very respectably, especially when we consider that perfection of definition is thrown away on composites. I thought of a mirror silvered on the front of the glass, but this would soon tarnish in the gaslight, so I did not try it. For safety against the admission of light unintentionally, I have a cap to the focusing-screen in the roof, and a slide in the fixed body of the instrument immediately behind the reflector and before the dark slide. ”

“ Beautiful as the Exposition is by day, it is at night that it becomes loveliest as a spectacle. Then it is a great glow of soft color, without shadow, but also without garishness. Never before has the attempt been made to light an exposition as this one is lighted. The highest standard before attained was a blaze of electric light secured by outlining the buildings with incandescent bulbs. That was the work of electricians. Here the illuminators are artists who have created a great picture of light and color. ”

“ These same rays may be collected and their intensity again increased.
Rays of light are reflected from one surface to another; Refracted, or bent, as they pass from the surface of one transparent medium to another; and Inflected, or turned from their course, by the attraction of opaque bodies. From the first we derive the principles on which mirrors are constructed; to the second we are indebted for the power of the lenses, and the blessings of sight,--for the light acts upon the retina of the eye in the same manner as on the lens of a camera. ”

“ A still more conclusive proof that we have to do with brightness discrimination, and that alone, in these experiments is furnished by the results of white- black tests made with an apparatus which was so arranged that light was transmitted into the two electric-boxes through a ground glass plate in the end of each box. No cardboards were used. The illumination of each box was controlled by changes in the position of the sources of light. ”

“ Every stage which has been advanced in artificial lighting has been welcomed in the home just as much as in the factory and in the workshop, for there are many daily duties as well as pleasures and amusements which are carried out much more satisfactorily when a good light is available than when there are shadows and dark corners only dimly lighted. ”

“ It is best, therefore, to arrange our colour schemes so that they will look harmonious in the daylight, and such colouring will not suffer much by artificial light, provided the room is well lighted by electric or incandescent gas lamps, and is not in a state of low illumination, or semi-darkness. ”

“ The student will, no doubt, at once perceive that if we concentrate the light of the sun upon an object, we shall also concentrate the heat, and either melt or consume it. A screen is therefore used in such cases, which will allow the light to pass while holding back the rays of heat. ”

“ So that all that building up of rings of glass is for the purpose of producing one fine and glorious lens of a large size, to send the rays all in one direction. Here is another apparatus used to pull the rays down to a Fig. 57.horizontal sheet of light, so that the mariner may see it as a constant and uniform fixed light. The former lamp is a revolving one, and the light is seen only at certain times, as the lenses move round, and these are the points which make them valuable in their application. ”

“ It is not enough to lay down a rule establishing the proportion which the surface of glass should bear to the number of pupils; attention must also be given to the direction whence the light comes to each pupil. The darkest point in the room must be light enough, and for this it is necessary that each desk shall receive a sufficiency of light direct from the sky. Every one who has practiced photography knows that the sky acts more strongly than any terrestrial body upon the sensitive surface. The least favored place in the room should be within the reach of this light. ”

“ This is simply an arc lamp with reflectors behind it and lenses in front of it. The whole apparatus is pivoted so as to be easily made to shine in any direction. The function of the lenses and the reflectors is to collect stray rays of light and send them all out in the same direction. This is shown in Fig. 103 where for simplicity the lens is represented as a single piece. L represents a point of light which will naturally send its rays out in all directions as the radii of a sphere; m, m, m represents a bright reflecting surface which is given that peculiar curve called a parabola. ”

“ The main conditions are to keep the light well to one side, that no direct rays pass through the lens to illuminate the screen, and to concentrate as bright a light as possible on the picture, and on that alone. ”

“ They are so arranged that the amount of light and heat transmitted can be reduced at will, so as to render the use of a dark glass unnecessary, thus enabling the observer to see all details in their natural colouring. ”

“ If, howover, the arrangement is slightly varied, so that transmitted instead of reflected light is made use of, comparatively feeble illumination is sufficient. A very effective way is to turn a small metal [Pg 190] disk, having an open sector of about 60°, in front of a sheet of ground or opal glass behind which is a lamp. By an arrangement of this kind upon a larger scale, the effect may easily be rendered visible to an audience. The eyes should not be allowed to follow the disk in its rotation, but should be directed steadily upon the centre. ”