Photography in Natural Colors
COLOR photography is not new. It has been the goal of ambitious inventors ever since scientists really understood something of the nature of light. Nearly all methods of making colored photographs are long and expensive. Though beautiful results were in some cases secured, only an able scientist could manipulate the apparatus, time the exposures, and keep track of the dozens of little things all-essential to securing satisfactory results. Even the Lumière process, widely employed as it is, is handicapped by the fact that the pictures must be viewed through glass.
Most of the previous processes were of the “three-color” type. That is, they depended on the fact that from three colors of the spectrum, red, yellow-green, and blue-violet, all other hues could be made by combination. Negatives of an object were made through red, yellow, and blue filters, and positives therefrom were colored and joined in various ways to make a resultant colored picture.
Within recent years encouraging experiments have been made which involve the use of two colors only, red and green. The most recent system of color photography dependant on this method is that of Mr. Percy D. Brewster of New York.
Two Plates Are Used with the Camera
The camera employed in the Brewster system and other two-color systems differs from the ordinary photographer’s mainly in that it has two plates instead of the customary one. The one directly back of the lens is known as the “green” plate; while the other at right angles is referred to as “red.” This arises from the fact that light rays reaching the “green” plate must first pass through a green filter, while those falling on the “red” plate are correspondingly filtered by a red glass. The “green” plate is intended to record at the green portion of the spectrum, while the “red” is sensitive to those at the opposite end.
The manner in which the image is conveyed to both plates is interesting. Thus, Mr. Brewster mounts a few inches back of the camera shutter, a mirror called the “Swiss Cheese” plate, its surface being at a 450 angle with the plane of the lens. The mirror is thus strangely named because it is full of holes, which serve to permit parts of the image to pass through to the “green” plate; the remainder being reflected by the solid part to the “red” plate. Inasmuch as images filtering through the holes overlap after passing the mirror, a complete picture is thrown on the “green” plate—and not a spotted one, as might be expected because of the holes. Likewise the solid portion throws a complete image on the “red” plate. Dividing the light between the two plates in this manner of course lengthens somewhat the time of exposure necessary; otherwise no other effects are ordinarily noticeable.
The same effect can be obtained in many other \tfays. Thus, in what is known as the “kodachrome” process a plate is employed which, instead of being perforated with Swiss cheese holes, is thinly platinized, so that it can both reflect and transmit light.
It is understood of course that negatives obtained with the Brewster, “Kodachrome,” and similar instruments are of the ordinary black-and-white variety —not colored in any way. The “green” plate differs from the ordinary negative only in the fact that it is especially dense where colors at the green end of the spectrum predominated, while the “red” plate likewise records densely roseate hues. From these two negatives positives are made on other plates by ordinary processes of contact printing. The image on the positive from the “green” plate is dyed red and that from the “red” plate green. The two positives are then placed face to face, and the image on one registered with the image on the other.
Hold the combined plates up to the light, and you can see the photographed object in its natural colors. It stands out from the background as striking as the original. The effect is startling, indeed.
Why Two Colors Must Be Employed
The reason for coloring the “green” positive red, and the “red” positive green, as mentioned in the foregoing, is
rather elusive and at the same time particularly interesting. Consider for instance the case of a red rose on a background of green leaves. The “green” negative upon development will be almost black where the green leaves appear on the plate, while the rose will be almost transparent. Similarly with the “red” negative, the rose will appear dense, while the green is recorded as a transparent area.
Positives from these two plates will in each case of course be just the opposite of the negatives. That is, a positive from the green plate will show the leaves transparent, and the rose dense; while that from the “red” plate will show the leaves dense, and the rose transparent. Dyes used in this process affect only the dense places. It is obvious that if you want a red rose to be red in the resultant picture, you will have to color the positive from the “green” negative red, that being the only one showing the red rose as a dense area. Similarly, you will have to color the positive from the green negative “red,” since in this case the leaves are dense. After dyeing them in this manner, the plates pass through a special process to eliminate the opaque black silver on the plates, leaving only the colored images. This process completed, the two plates are placed face to face and registered properly. Then you see the red rose in its proper place among the green leaves.
The next step is to cement these two positive emulsions together. This done, they are stripped from the glass and transferred to paper, canvas, ivory (in the case of a miniature), or any other backing. In their new positions they look not unlike an oil painting, especially when canvas is used as a mount.
For the sake of simplicity, the foregoing description of the red rose and green background referred only to these two colors. It is understood of course that almost any color which may have been present in the original object also appears in the finished picture. This is possible because red and green combined in different proportions by the process here used will give such desired colors.
How a Steamer’s Engine-Room Is Ventilated
PHYSIOLOGISTS have shown in recent years that the chief effect of ventilation and open air treatment depends on the movement, temperature and moisture of the air, and less upon its chemical properties than was expected. For this reason the cooling of overheated engine-rooms, underground or underdeck, is best obtained, as engineers have discovered, by flooding them with fresh air from outside under slight pressure. This positive ventilation or a continuous change of air also removes all noxious gases and smells emanating from the oil and bilges.
The accompanying drawing shows a transverse sectional view of the engine-room of the “Aquitania,” with the recommended method for flooding the confined space with cool, fresh air under moderate pressure.
The air is delivered
into the engine-room by a large open fan placed at the junction of the lower ends of the air-shafts, so that the full volume of fresh air, equal in this instance to about one hundred and fifty thousand cubic feet per minute, is propelled into and properly distributed through the engine-room without lossfromdeliveryducts.
When desirable, the air in the engine-
room may be changed one hundred and twenty times an hourwithout uncomfortable drafts. The cool air is drawn, not forced, down from the upper deck and delivered laterally by open fans placed low down in the engine-room so as to flood the whole space with air, the cooler incoming air falling towards the floor, displacing the heated air and expelling it up the main hatch. Many transatlantic liners have the ventilating system illustrated.
What Inventors Are Doing for the Fisherman
A Watch-Like Coin-Case
THE market offers so many coincases, embodying every kind of advantage, that it seems impossible to make any improvements. For all that
a new one has been invented, which has the shape of a watch so that it may be carried on a chain. It holds eight coins of the same denomination. A central disk, its periphery cut to form eight -ratchetteeth, rotates about a short shaft secured in the watch-like casing. A spring is fastened at one end to the shaft about which it is wound, and at the other end to a pin in the disk. The disk has eight radial flanges. Four flanges project from one side of the disk and four from the opposite side, alternately.
The casing has two lateral, bulging parts to accommodate two pawls which operate the disk. Each pawl consists of two fingers projecting in opposite directions from a central shaft. The one is held against the ratchet-tooth by a tiny spring, and the other acts as a stop to the adjacent tooth. The shorter one has a finger-button which projects through a slot in the case. On the under side of the outer case is a wide slot for receiving and discharging coins. The coins are alternately inserted one at a time at opposite sides of the disk, this action automatically winding the spring.
Mosquitoes on Snow Banks
IN both the Rocky Mountains and Alaska the geologists and engineers of the United States Geological Survey have as part of their regular equipment mosquito-nets for their heads. Even when working in deep snow, head nets and gauntlets are necessary to protect the field men from the blood-thirstiness of the pests. The mosquito does not vanish with increasing altitude. At eleven thousand feet, or timberline, he is as prolific as at sea-level, and smoke, no matter how dense and pungent it may be, will not eradicate him. The only sure relief lies in the net. In some sections of Colorado the mountain natives let mosquitoes bite them until their systems become thoroughly inoculated with their poison. After this they are bothered no more. The first advice
given to the “tenderfoot” by the oldtimer is, “Let ’em bite; they won’t keep it up long.”
An Improved Vegetable-Slicer
AVEGETABLE-SLICER which can be adjusted to cut anything into tiny shreds, from a carrot to a cabbage, may be described as follows:
An annular base, mounted on feet, has several roller bearings journaled on the inner side of its rim. Resting on this base, and attached to it by clamps, is a cylindrical hopper. A cutting-disk is provided with three or more slots, radially cut, with a corresponding number of blades, which can be adjusted at their edges. There are also a like number of splitter-knives which assist in cutting up the vegetables. When in position in the machine the disk rests on the roller bearings and is rotated by a handle-shaft. Fitting around the vertical shaft is a tube or hub from which radiate four or more partitions, thus dividing the hopper into four or more compartments.
When the vegetables are placed in the hopper the action of the cuttingdisk beneath them gradually slices away the whole vegetable, the particles falling through the slots into a dish. Not only
the size and number of the blades can be adjusted, but the plates which form the chambers are made to fit into grooves on the cefitral hub and inner surface of the hopper, so that they slide in and out very easily. Thus small vegetables, large vegetables or both may be sliced at one time.
Fish Hatched in Artesian Basin
ONE of the most unique and convenient fish hatcheries of the government is located near Laramie, Wyoming, where sources of good water are few
and far between, the region being semidesert. This hatchery is an artificial pond fed by a never-failing artesian well which flows of course night and day. The water comes from a considerable depth and is therefore pure and cool. It is claimed that better results are obtained from raising trout from this hatchery than when ordinary surface water is used. The float in the center of the pond serves as a shady nook in which the young trout can find a cool, shadowed retreat such as this game fish delights in. When the little trout have attained the proper size they are taken out and used to stock the streams in the vicinity. After the water has served its purpose as a trout breeder it flows off through pipes and is used to irrigate the little ranch farmed by the keeper of the hatchery.