TN: Triplexicon Lantern.
and is provided with the patent triplex wick, which affords the utmost illumination obtainable with any oil light. The back and front of the hood are closed interiorly by glass plates, specially annealed to withstand extreme heat, and the rear one is again closed by perforated sheet iron, covered interiorly with a highly polished metallic reflector, back of which is inserted an eye piece of ruby glass. The latter enables one to always observe the condition of the flame and wicks, and regulate them without disturbing or discontinuing the action of the instrument. The chimney is made telescopic, to pack more compactly."
"The diffusing lens, specially constructed for the purpose, is mounted on a cylindrical slide to extend, ifp200necessary, the focal distance, while the condensing lenses, which are of four inch diameter and can be separated for cleaning, are inserted in a corresponding slide within the wooden case.
"The case itself is quite compact, and appears very ornamental in its highly polished mahogany, with its little bronzed ventilators on either side at the bottom. The metal front is burnished and has a spiral spring adapter for the admission of the slides. A substantial wooden box contains all, and serves also as a table for the instrument while in use. Altogether this is the finest example of its kind we have yet seen; it will also serve admirably for enlargements with the gelatino-bromide paper."
The pictures prepared for projection by the magic lantern are made on glass of one size, invariably 3¼×4 inches, and are copies of negatives made by transmitted light and by two methods. When the negative is made by the detective, or pocket cameras and on plates 3¼×4¼, the positives or slides may be made by contact printing; that is, the prepared plate is placed in contact with the negative, film sides together or touching in a printing frame, the back pressed closely down and the plate exposed to the light of a gas or lamp flame—daylight is too strong—for from five to ten seconds, according to the density of the negative; the plate is then developed perfectly with ferrous oxalate until the picture is seen clearly on the surface; when the shadows have become sufficiently dense, or before there is any discoloration of the high lights, remove and wash and fix in hypo and alum. (See Roche's formulap201in article on Transparencies.) Remember that all parts of the pictures that represent the whites should be clear glass.
When the negative is larger than the slide, then the copy must be made in the Camera. (See article on transparencies.)
It is claimed by some that slides made by the collodion process are superior to those made on dry plates, but in my own personal experience I have found Anthony's transparency dry plates superior to all others and better than collodion.
To protect the film surface of the slide, thin, clear glass of a corresponding size is placed against the film surface with a paper mat (the opening of which should closely correspond with the outline of the picture) between, and the two bound together neatly with adhesive paper.
Collodio chloride is a collodion emulsion, consisting of plain collodion and silver chloride. It is a grayish-white substance in liquid form, and being quite sensitive to light, it must be kept in a covered bottle.
Anthony's collodio chloride is supplied in 8-ounce or larger bottles, and will keep indefinitely. The formula for its preparation is not known, but it is sold at a price that renders its preparation by individuals unprofitable.
The following formula will give a superior quality of collodio chloride to those wishing to make their own.
No. 1.
p202
No. 2.
No. 3.
To 2 oz. plain collodion add of
By the use of this emulsion most beautiful pictures may be made on paper and upon porcelain, opal, stoneware, and other plain white surfaces.
When paper or any other flexible surface is to be used, it is simply coated with the emulsion. First place the paper flat upon a square of glass and pour upon it the emulsion, causing it to flow evenly over the whole surface and the excess to flow back into the bottle from the lower corner. This must be done in a subdued light, but not necessarily in a dark room or by non-actinic light, as in the case of the use of gelatine bromide paper.
When the paper is coated it should be placed in a closet or some dark place to dry, and when dried it is printed in the same manner as silver paper, by placing it in a printing frame in contact with a negative. It is printed by sunlight, and may be examined while printing, to see the progress made. The printing should be carried a shade or two beyond the color suitable for a finished print, and when done should be washed in clean water and toned with gold, and afterwards fixed in hyposulphite soda and again well washed in the same manner as for silver prints.
Flat porcelain or other enameled surfaces, beforep203being coated with the emulsion should be albumenized in the same manner as glass plates for the collodion process.
The white of an egg to 6 ounces of water, well beaten, will be the most suitable proportion for this purpose.
For printing on porcelain or other enamel plane surfaces, specially prepared printing frames are necessary in order that the progress of the printing may be ascertained.
All articles with uneven surfaces, such as plaques, plates, saucers, of porcelain china or stoneware, that cannot be placed in printing frames, may have pictures printed on them by the aid of the Solar Camera or by Anthony's Enlarging Camera, and the lime or the magnesium light.
See Anthony's Enlarging Camera.
THE ENLARGING CAMERAMethod of making large pictures from small negatives.TN: The Enlarging Camera.
THE ENLARGING CAMERAMethod of making large pictures from small negatives.
p204
The prevalent use of the Detective Camera, and other cameras, for making pictures on small plates, has caused a demand for an apparatus whereby large pictures may be produced from such negatives.
This demand has been met by the production of Anthony's New Enlarging Camera in connection with the Gelatino bromide papers.
This enlarging box is at once simple and effective. It consists of a black wooden box containing a good kerosene lamp. The sides of the box have a number of grooves that carry a slide holding a large condensing lens, O, while another slide holds the negative, N, that is to be printed.
TN: Schematic of the Enlarging Box.
To the outside of one end of the box is attached a sliding bellows, and an objective, E, by which the picture is enlarged and thrown upon any white surface. In a few words, the enlarging box is a small solar camera, but using artificial light instead of the sun's rays; or it is a magic lantern so arranged that no light can come out of it except that which passes through the objective.p205
The use of the instrument is as simple as its construction. The lamp is lighted, and then adjusted in the box so that a shadowless circle of light is projected upon a white wall or other surface, all the light being utilized by means of the reflectors situated back of the lamp. This adjustment is effected by moving the condensing lens and the lamp nearer or farther apart. It is perhaps best to place the condenser in a groove near the objective, but sufficiently far from the end of the box to allow the slide containing the negative to be inserted. Having obtained a good circle of light, now place the negative in the slide and adjust the slide in the box so that it is between the condensing lens and the objective, and as close to former as may be. By means of the objective a good focus is now obtained, and we are ready for an enlargement.
With this apparatus and an artificial light, of course rapid printing paper is necessary. The cap is placed on the objective, and by the aid of red light a piece of the gelatino bromide paper is adjusted on the surface where the image was projected from the enlarging box. This part of the operation maybe assisted by removing the cap from the objective and placing a piece of ruby glass before it, allowing the image to fall on the paper through the ruby glass. A simple and effective way of holding the paper is to tack two common wooden laths upon a board in such a way that they will serve to hold the paper along two of its longer sides, in which case the board must be used to focus upon.
The exposure necessary will depend upon the density and character of the negative. With a medium density in a portrait negative, one minute appears sufficient, but something also depends upon the paperp206used, those of English manufacture being rather slow. With a little care and this little contrivance much pleasure and success are attainable in enlarging pictures from small negatives.
The use of the new "tooth" surface printing paper admits of the application of crayons to the enlargements.
By substituting the lime or the magnesium light for the kerosene lamps, pictures may be printed by the collodio chloride process upon a variety of uneven surfaces, such as plaques, plate, saucers, pots, etc., etc.
In fact, this instrument might very easily be converted into a solar camera by fixing it in a window and adjusting a mirror outside that would reflect the sun's rays into the condenser within the box.
Having coated a plate with the common negative collodion and excited it in the usual nitrate of silver negative bath, expose it to the light for about a second at the door of the dark room, wash it and then apply to the surface as a wash a solution of
The plate is now ready for exposure in the enlarging camera; the lime or the magnesium light being sufficiently powerful for the purpose. On its removal from the camera the plate is washed, immersed for a brief period in the nitrate of silver bath, or otherwise treated with a solution of this salt, after which the image is developed by the ordinary developing solutionp207for wet plates. In this way is obtained an enlarged negative from a small one without the necessity of an intermediary transparency.
The discovery that certain of the per salts of iron when exposed to light undergo decomposition and are reduced to proto salts, is attributed to Sir John Herschell. But we are indebted to Poitevin for numerous interesting developments in this department.
For instance, the per-chloride so exposed becomes reduced to the proto-chloride; or, as Von Monckhoven more appropriately remarks, to the state of oxy-chloride. For this purpose the sesqui-chloride must be quite neutral. The ammonia tartrate, potassa tartrate and the ammonia citrate of iron are much more sensitive to light than the sesqui-chloride, and the latter salt (ammonia citrate) most of all.
The image formed by means of these salts is much fainter than that with the chloride of silver; but it can be intensified by the application of other metallic salts.
The mode of operation consists in floating the paper on the solutions in question in the dark room, in allowing them to dry, and then exposing them afterward beneath a negative, as usual with paper prepared with chloride of silver.
The preparation of the paper by this process is very simple, and requires very few manipulations, while the results, when prints are made, are pleasing and lasting. Prints in blue are so easily made as to bep208extremely convenient for making proofs from negatives, and they are well adapted for mottoes, plans, drawings, manuscript, circulars, and for representations of scenery, boats, machinery, etc., etc., and for engravers' use.
Ferro-prussiate paper can be procured from E. & H. T. Anthony & Co., or can be easily made by the following formula:
Float the paper until it lies quite flat upon a solution prepared as follows:
When these two are dissolved, mix them together and filter into a clean bottle.
The solution should not be exposed to a strong light, and the paper must be floated on it in a very subdued light, and in the same manner as paper is floated on a silver solution. When it no longer curls, but lies flat on the solution, take it by the corners and raise it slowly from contact, and hang it up to dry in a dark place. When dry, it can be used at once, or may be kept for future use by rolling it, prepared surface in, and placing it in a tin box or other receptacle, free from light and dampness.
To make a print on this paper, place the prepared surface in contact with the negative in a printing frame and expose to sunlight.
The time of exposure will vary according to the density of the negative and the intensity of the light. The rule is to allow the light to act long enough for the portions which first turn blue to become gray, withp209a slight metallic luster. At this point remove the paper from the frame and place it in a dish of clean water.
It now gradually becomes a rich blue throughout, except the parts which should remain white. Change the water from time to time, until there remains no discoloration in the whites; dry, and the picture requires no further treatment.
The blue color may be totally removed at any time by placing the print in ammonia water.
This is the standard formula.
Float the paper for a minute in a solution of
Dry in a dark room, and then expose beneath a negative until the dark shades have assumed a deep blue color, then immerse the print in a solution of
Wash the print, and then immerse it in a hot solution of
Wash again, and dry.
Float the paper on a solution of the sesqui-chloride of iron. Dry and expose, afterwards wash the prints, and then immerse them in a bath of ferrid cyanide of potash. The picture will appear of a blue color in all those places where the sun has acted.p210
The paper, without having undergone any preceding preparation, except that of having been excluded from the light for several days, is floated on a bath of the nitrate of uranium as follows:
The paper is left on the bath for four or five minutes, it is then removed, hung up and dried in the dark room. So prepared, it can be kept for a considerable time.
The exposure beneath a negative varies from one minute to several minutes in the rays of the sun, and from a quarter of an hour to an hour in diffused light. The image which is thus produced is not very distinct, but comes out in strong contrast when developed as follows:
The development is very rapid in this solution. In about half a minute it is complete. As soon as the picture appears in perfect contrast, the print is taken out and fixed by immersion in water, in which it is thoroughly washed.
This is a more rapid developer than the preceding. The print is fixed in like manner by water, in which it must be well washed, and afterwards dried. When dried by artificial heat, the vigor of the print is increased.p211Prints that have been developed by the solution of nitrate of silver may be immersed in the gold bath, which improves their tone.
The picture may be developed, also, by immersing the prints in a saturated solution of bichloride of mercury and afterwards in one of nitrate of silver. In this case, however, the times of exposure must be increased.
Pictures may be obtained, also, by floating the papers on a mixture of equal quantities of nitrate of silver and nitrate of uranium in about six times their weight of water.
When dry, they are exposed beneath a negative. In this case the image appears, as in the positive printing process, with chloride of silver, being effected by the decomposition of the nitrate of uranium, which, reacting on the nitrate of silver, decomposes this salt and reduces the silver. These prints require fixing in the ordinary bath of hyposulphite of soda, and then washing, as usual.
Float the papers for four minutes in the preceding bath of nitrate of uranium, drain and dry. Next, expose beneath a negative for eight or ten minutes, then wash and immerse in a bath of
In a few minutes the picture will appear of a red color, which is fixed by washing thoroughly in water.
Immerse the red picture, before it is dry, in a solution ofp212
The tone will soon change to green; fix in water, wash and dry before the fire.
Float the paper for three or four minutes on a bath of:
Afterward take them out and dry. An exposure of ten or fifteen minutes will cause the necessary reduction; the picture has a beautiful violet color consisting of metallic gold. Wash and dry.
Photography, throughout its varied range, produces no more charming or satisfying picture than the transparency, whether it is on glass for the window, or on porcelain or opal for the lamp.
The beautiful and sparkling gradation of light and shade, the variety and depth and richness of tone and color inherent in a fine example of this picture, renders it most positively "a thing of beauty and a joy forever,"
It is a picture made by a peculiarly simple and easy process, the most exalted expressions of which have always commanded the popular favor and a high price, and the working of which has, both for the amateur and the professional photographer, the highest interest and attractiveness. By no other method or process can the amateur succeed in producing pictures ofp213equal excellence, with the same outlay of time and skill, which is a peculiarly fortunate circumstance, as the tendency among amateurs at this time is to form themselves into clubs and societies for the exchange of their most beautiful and successful efforts as picture makers. And an exchange in the form of a transparency enables the receiver to command all other styles of pictures, through the negative that may be produced from it.
The production of these pictures has assumed such importance already as to have called forth a special dry plate for making transparencies, to say nothing of the other special goods for the same line, such as metal frames, ground, engraved and etched glass for mounting, the beautiful borders of which greatly enhance the beauty and elegance of the finished picture.
Transparencies are adaptable for the exhibition of every kind of picture that can be copied; paintings, engravings, portraits, landscapes, all become equally acceptable when skilfully finished and properly displayed.
By this process, also, the amateur is enabled to provide himself with slides for his magic lantern and to have the satisfaction of exhibiting to his friends the trophies of his own skill in the use of the camera and the developing solution.
The amateur, in order to succeed in producing high class work, should possess himself of one of Anthony's duplicating and copying cameras, so that he may be enabled to avail himself of both methods of work; that is to say, by the camera and by contact printing, as by the latter method he is restricted to the range and size of his negatives, while by aid of the camera he is enabled to copy all kinds of pictures to acceptable sizes,p214and he can make his transparencies of equal size with his negative, or vary the size to suit the requirements of the case.
The use of the duplicating and copying camera is fully detailed in the article on Duplicating Negatives. By its use the amateur is enabled to work by the wet collodion process, which has many advantages, or by the dry plate process, using Anthony's transparency plates or the gelatino albumen plates made in Philadelphia. If he confines himself to contact printing, he is restricted to the use of dry plates only.
The outfit of goods for making and finishing transparencies consists of:
When making transparencies by contact use artificial light, either gas or a common lamp. A deep printing frame is the most suitable, having a piece of thin plate glass in it to support the negative. Lay the negative down with the film side up, place upon it the dry plate, put in the back and press firmly down with the springs; expose to gas light from six to ten seconds at a distance of twelve to fourteen inches; expose longer to lamp light, say from ten to twenty seconds, or the duration of time that may be considered sufficient, judging from the density of the negative in use.p215
The time of exposure and the strength of the developers are the most important factors in determining the quality and tone of the resulting transparency. Giving a short exposure and using a strong developer will ensure a vigorous picture with a rich velvety black tone. A long exposure, necessitating a weak developer, will produce fine gradation of light and shade, clear shadows and a warm brown tone.
When making transparencies for the window, cut a mask, with an opening, allowing for the border or margin on the ground glass it is intended to use. A suitable paper for this purpose is of deep orange color and moderately heavy; place the mask between the negative and the dry plate to be acted on, and it will protect the margin from the action of light, leaving it clear glass, and so exhibiting to better advantage the ornamented border of the ground or etched glass, which is placed against and covers and protects the film of the dry plate. When making lantern slides the mask is not necessary.
No. 1.
No. 2.
When about to use, mix equal parts of Nos. 1 and 2, always pouring No. 1 into No. 2.p216
The exposure having been made in the camera or in the printing frame, place the plate in the developing tray and pour upon it sufficient of the developing solution, mixed as directed, to cover the plate at once, and keep it in motion from time to time. Develop until detail in the high lights is plainly visible. When this is the case remove the plate, wash well and fix in hypo-solution.
When the plate is quite cleared, of which it is better to make sure by leaving the plate in the fixing solution for fully five minutes after it first appears clear, remove it and wash again very thoroughly, and then immerse it in the clearing solution.
Leave the plate in the clearing solution two minutes or more, then wash again, rubbing the surface lightly with a tuft of cotton to remove any sediment that may adhere to the film, then set it up in a rack to dry.
may be developed in the same manner until detail may be seen in the face, if it is a portrait; then remove it and instantly flow with a solution of bromide of ammonium to stop developing action, then wash, fix and dry as before.
For portraits on porcelain or opal, to be viewed as positives by reflected light, develop until the fine half-tones in the face are visible. When they are for transparencies,p217either for window or lamp shades, develop until the detail in the high lights of portrait or landscape are well out. This may necessitate a longer exposure by lamp-light.
Transparencies developed by other methods receive a stain or color, which, in many cases, is not unpleasing; for instance, the following formula will give a very beautiful yellowish color:
This will cover and develop one 8×10 plate, giving it an agreeable color similar to that produced by development by sal soda and pyro, but much more agreeable.
A very fine blue color is imparted to the plate when developed by the following formula:
From the fact that these different developments impart different colors to the negatives, it might be inferred that the gelatine film is susceptible of receiving color from a stain or dye; if such is the case, transparencies may be made in every color of the chromatic or solar spectrum. I have seen one of a beautiful rose color, and was informed that the color was received in development.p218This was possibly so, but it is very easily ascertained if the film of the developed plate is capable of receiving a dye of any pleasing color suitable to the subject.
Transparencies for the decoration of windows, or gas shades, or for examination in the stereoscope, differ from those intended for lantern projection in being somewhat more intense. A lantern transparency must have its high lights of pure glass; in the case of the others, it is of less consequence, should they be slightly shaded.
To produce a transparency by wet collodion, a camera is required the body of which will be capable of extending to twice the focus of the lens, although a still further extension is desirable. The reason for this lies in the fact that when making a transparency the same size as the negative, the sensitive plate must be withdrawn from the lens to the extent of precisely twice the solar focus. It occasionally happens that it is desirable to make the image in the transparency on a scale a little larger than that in the negative. To permit of this being done, it is necessary that the distance between the sensitive plate and the lens be increased, for according to this distance, so is the amount of enlarging.
The negative must be so arranged as to have a clear sky or a uniform light behind it. If the work is to be effected at a south window into which the sun is shining, the requisite uniformity of illumination is obtained by placing a sheet of ground glass within a few inches of the negative. Arrangements must be made byp219which the negative may not only be held rigidly in an upright position, but that such adjustments may also be made as will bring it as near to or as far from the lens as will be found requisite, and also as will permit of its being raised, lowered or having any part far removed from the centre brought into the axis of the lens. These conditions are fulfilled in all good transparency cameras. We do not assert that a properly constructed camera for the special purpose of making transparencies is an absolute necessity, seeing that a light framework erected in front of the camera, and with which it need not be connected with a bellows body, will suffice, but the great convenience of a camera expressly for the purpose cannot be overrated.
In order to ensure clearness of the high lights, the collodion should be rendered of a dark sherry color by the addition of a few drops of an alcoholic solution of iodine. The strength of the solution is not of consequence, but enough must be added to the collodion to render it of the color indicated. Collodion for this purpose works rather better after it has been kept for a few weeks or months than when it is quite new. No hints can here be given as to the length of exposure requisite, but if the camera be pointed to a moderately bright sky, the negative one of average density, and the lens worked with a small diaphragm, an exposure of twenty-five or thirty seconds may be given, and, by noting carefully the quality of the resulting picture when finished, the data for a more accurate timing of the exposure may be ascertained therefrom.
After developing the image with iron, if it should, upon examination prove to be too thin, wash off the developer and apply pyrogallic acid and silver and bring it up to the required intensity. Fix and wash.p220
At this stage—that is, after fixing and previous to the plate being dried—the image may be toned to almost any desired color. It is to be regretted that some of the most desirable tones cannot be recommended, on account of the want of permanence. A type of the best of this class of toning agents is as follows: Make a saturated solution of bi-chloride of mercury in hydrochloric acid and dilute it with twelve volumes of water. Into this place the plate, after having thoroughly removed the hyposulphite by washing. When it has become quite bleached, wash carefully again and place in a bath composed of a dram of sulphide of ammonium to a pint of water.
The image will soon acquire a rich dark brown color, and when this is found to have penetrated the film, it may be washed, dried and varnished.
A solution of sulphide of potassium imparts a good brown color.
Chloride of gold gives a tone which may be described as a neutral black, that is both durable and very pleasing for quite a variety of subjects.
A solution of chloride of platinum gives a tone which is very permanent. It is essential when using either gold or platinum that the toning solution be weak.
It is possible, however, so to develop a collodion transparency as to obtain a rich purple black tone without any after toning. The addition of a few drops of a saturated solution of citric acid per ounce of developer effects this, but as it checks development at the same time, the proportion of protosulphate of iron must be increased to such an extent as to impart energy to the developer.p221
A few drops of a solution of gelatine in sulphuric acid is also of great utility when added to an iron developer. It promotes clearness of image and richness of tone.
ANTHONY'S BICYCLE CAMERA.ANTHONY'S BICYCLE CAMERA.
ANTHONY'S BICYCLE CAMERA.
p222
How delightful a pleasure it is in the early morning, or of a fine afternoon, to mount a bicycle and take a spin along the country roads.
The bracing air, the easy motion, the sense of independence, so act upon the mind as to make it keenly sensitive to the beauties of the foliage and scenery that so swiftly pass before the eyes. Such must have been the thought of him who penned the following:
"Most of us, no doubt, have experienced the desire, as our machines have passed some pretty and specially picturesque bits of scenery, to take away with us some memory, to be recalled at some future time, of what we were then passing by. And most of us have also experienced the difficulty, as one picturesque scene is replaced by another, and so on to the end of our journey, of preventing the many scenes getting somewhat blended in our minds, and an inability to produce details with accuracy. To sit and sketch such scenes would be to reduce the journey to a sketching tour, and the distance to be covered must be reduced accordingly, thus depriving the 'cyclist' of the usefulness of his machine.
"That which this tourist desires may be accomplished by the aid of photography, and the whole addition to the impedimenta of the 'cyclist' can be so arranged as to be trifling.
"The apparatus consists of a tripod, camera and case. My camera, with leather case and provisions for exposing a dozen 5×4 plates, weighs between fourteen and fifteen pounds.
"I have endeavored to show in the brief space of timep223at my disposal, how the enjoyment of a 'cyclist's' ramble may be enhanced by that most wonderful combination of chemistry, optics and mechanics, which has resulted in placing the science of photography within the reach of the amateur.
"When we have imprisoned our sun pictures, and have them safe, though latent and invisible, intangible and impalpable to any of our senses, we may at our leisure (it may be months after), by means of those marvelous chemical affinities which throw the haloid salts of silver again into chemical life, produce on the film the pictures we have so desired; and then again, by further use of the light, we print our scenes on the sensitive paper. We have then a pictorial history of our journey in our albums, which will recall the pleasant memories of happy days spent long, long years ago."Frank Cobb."
"Frank Cobb."
The amateur who wrote as above rode on a tricycle and carried a load of apparatus for 4×5 plates, amounting to fourteen or fifteen pounds, for a dozen pictures. That is the way it is done in England; but in this country mechanical skill has reduced that load to less than five pounds for two dozen pictures of the same size, and the cyclist goes forth with a small camera and a roll-holder charged with films for 24 exposures, which are carried in a small case supported by a strap passing over the shoulder, and these films are so sensitive that it is not necessary that he should dismount and undergo the trouble of erecting a tripod, and attaching his camera thereto. He has only to fix his camera by a universal joint to his steering-bar and shoot as he flies, with the full confidence that at the proper timep224he will find his bit of scenery spring into beauty and brilliancy under the influence of the developing solution. Or if the exigencies of the situation require that the point of view would be better off the road, then the wheel is very easily converted into a support for the camera by the little brass telescopic rod which is adjusted against the pedal at the side of the wheel by a strap, and lengthened to reach the ground, against which the wheel may rest quite sufficiently steady for all purposes in question.
The little camera, with double holder telescopic support for wheel and the case, will weigh about two pounds, which may be carried by means of a strap on the shoulder, or may be buckled to the saddle of the machine.
The detective camera, also, is quite well suited for such a purpose, with the roll-holders or otherwise, as may be desired; but the paper films are more sensitive than the plate, and are, therefore, more suitable for such rapid work as may be required.
If you place any natural object at a distance from a convex lens, a much smaller image of the same will appear at the focus of the lens. When this small image is reduced to that point that it cannot be seen clearly with the naked eye, and is photographed, it may be called a micro-photograph. On the contrary, if the object is a microscopic one, and is placed at a point very near a convex lens, an enlarged image may be found at a considerable distance from the lens. A photograph of this enlarged image of a microscopic prepared object, is termed a photo-micrograph.p225
Some confusion among so-called authorities on this subject renders their definition of sufficient importance to be given in this connection.
With the former we have nothing to do, as there can be very little interest attaching to the production of pictures of any object on so small a scale as to require a microscope to look at them.
With the latter, however, it is otherwise, for by the aid of photo-micrography we are enabled to place in permanency for closer study those enlargements of natural objects that are revealed to the human eye by the microscope. The secrets of the composition of the drop of water and a knowledge of its "monstrous and terrific inhabitants," are thus made known.
Previous to the introduction of the sensitive dry plate the practice of photo-micrography was confined almost wholly to those possessed of leisure, and ample means to provide the expensive and complicated instruments necessary, or to savants like Dr. Woodward, backed by the resources of a liberal government supplying apparatus and appliances far beyond the means of the ordinary student of natural science.
The advent of the gelatine dry plate placed the workers in this branch of scientific research more nearly on a level, at least as far as the possession of suitable and efficient instruments are concerned, and one of these workers has published for the instruction of amateurs and others a very valuable article on photo-micrography, from which we extract by permission a description of the instruments necessary to the successful practice of this interesting study.
Mr. Walmsley, in the article referred to, says: I will now describe the apparatus I am using at present,p226passing unnoticed the various stages by which its comparative perfection has been reached. Four essential parts make up the complete outfit.
A microscope with a joint to the body permitting the same to be inclined to a horizontal position may be employed, but the essentials to accurate, comfortable work are as follows:
A heavy, solid stand, perfectly firm in all its positions, with a short body (the 6-inch Continental model is admirable), good coarse adjustment for focus, and a very delicate, fine one, the latter controlled by a large milled head, in the periphery of which a groove is turned to admit the focussing cord, hereafter to be described. A solid, mechanical stage rotating in the optic axis, and a sub-stage moved by rack and pinion, capable of carrying an achromatic condenser, polariscope, etc., are almost indispensable. The objectives should be the very best, especially corrected for photography in all powers under the one-fifth of an inch and of moderate angular aperture.
Perfect corrections of chromatic and spherical aberrations, with the greatest penetrating and defining powers, are essential features in objectives designed for photography.
A binocular microscope can be used quite as well as a monocular, by simply shifting the prism, but if an instrument is to be selected purposely for photographing,p227the latter is recommended in preference to the former. In either case, the tube is to be lined with black velvet or flock paper, otherwise there will be a reflection from its inner surface, which will cause a ghost in the negative. An accurately centered double or triple nose-piece, carrying as many objectives of different powers, will also be found an immense convenience, saving much time and labor in choosing the proper object glass for any particular object. I use a triple nose-piece, upon which are always screwed a two-thirds, a four-tenths, and a one-fifth inch objective, being the powers most generally used. If the one-fifth is to be employed in making an exposure, the object is readily brought into the centre of the field under the two-thirds by a simple rotation of the nose-piece; the one-fifth is now brought into position, when the object will be found to occupy the centre of its field of view. Much valuable time, which would otherwise be expended in finding a minute object under so considerable a power, is thus saved.
Most chemical crystals being colorless and nearly invisible under ordinary illumination, require to be examined and photographed by polarized light. For this purpose, the polariscope prisms should be of large size, and both mounted in revolving settings. The lower prism should also fit into a sub-stage, capable of carrying an achromatic condenser above, in order to properly illuminate the field with any objective above the two-thirds inch. The achromatic condenser itself should consist of at least two combinations of different powers and of wide angular apertures. It is always necessary to employ a condenser of greater power than the objective. If a one-fifth is used, thep228illumination should be by a four-tenths to get the best results, whilst a one-tenth should be illuminated by a one-fifth. For lower powers, the ordinary bull's-eye condenser, in connection with a diaphragm of varying apertures, will be found all-sufficient.
For the great majority of workers the following powers of object glasses are recommended: Two inch or one and one-half inch, two-third inch, four-tenth inch, one-fifth inch and one-tenth inch, the latter an immersion capable of being used with glycerine, since water evaporates too rapidly for practical use. With these powers, and a camera having thirty inches extension of bellows, a range of powers from about ten to six hundred diameters may be obtained, whilst the addition of an achromatic amplifier will increase the power of the one-tenth to more than one thousand diameters, without perceptible loss of light or definition.
All the foregoing features are combined in the microscope I am using for this work, and, in enumerating them, I have but described that very perfect and complete instrument. We pass now to the second part of our outfit.
Probably the most convenient and generally useful form of camera is one with bellows extending some thirty inches, and capable of carrying both quarter and half sized plates, horizontally or vertically. My box is a square one, carrying plates from the 4-4 size (6½×8½ inches) down to 3¼×4¼. The bellows are in three divisions, extending fully four feet, giving altogether nearly six feet from the microscopic stagep229to the focussing screen when fully drawn out. It is very carefully made of hard wood, and the framework carrying the bellows moves with the utmost smoothness upon its Λ-shaped runners. A short cone front receives the microscope tube, and all extraneous light is shut out by a wrapping of black velveteen around the opening, secured by a rubber band. The focussing screen (which is only used for arranging the object in the centre of the field or plate, and is entirely removable) has a space of the precise size and shape of a lantern slide pencilled in its centre, as a guide to the making of quarter plate negatives. An object filling this space on the ground glass will necessarily occupy the same position on the quarter plate when the holder containing the latter is made to take the place of the focussing screen.
As stated, the ground glass is used only for containing the object, and for coarse adjustment of focus. It is impossible to grind it finely enough to accurately focus any delicate tissue with high or even moderate powers. Many suggestions have been made and devices used, but all I have tried proved unsatisfactory, until the following appeared in an English journal:
An evenly coated gelatine plate is to be exposed to a flood of white light, developed to a very slight intensity—a mere smokiness—fixed and washed as usual, then bleached with mercury, washed and dried. The result is the most perfect focussing surface imaginable. To use, remove the focussing screen from the camera and replace it with the plate holder from which the slides have been removed. The bleached gelatine plate (which of course must be of proper size to fit the holder) is to be placed therein with the film sidep230toward the microscope. Now place a focussing glass against the back of the plate, apply the eye to it and adjust the focus by a delicate pull of the cord. Nothing can be more satisfactory. When the proper adjustment is determined upon, secure it from possible change during exposure, by winding the cord once or twice over the screw eye at the rear of the camera frame.
The plate holder (single) opens at the back to receive the plate, and being square, like the camera box, admits of the negative being taken vertically or horizontally, as may be desired, a matter of no small importance in many cases.
This feature, in connection with the revolving stage, enables one to place any object upon the plate in the best position for printing. The full size of the plate carried by my holders is 6½×8½ inches, but by the employment of removeable rabbett kits, plates 5×7, 4×5 and 3¼×4¼ can be used. It is desirable to have two or three additional holders as time savers.
For our work to possess any real uniformity or value, it is absolutely necessary that the magnifying power used with each exposure should be ascertained and noted. To make measurements each time would be a waste of that precious commodity, to avoid which I have adopted the following device:
The bed or framework upon which the bellows extends, is divided into spaces of one inch, and the same plainly marked thereon. Suppose this extension is thirty inches, and that by means of the stage micro-meter we find the one and one-half inch objective to magnify twenty diameters with the bellows closed and fifty fully extended. This gives the value of one diameterp231to each inch of bellows drawn out, and if the magnified object reaches the desired dimensions, at, say twenty inches extension, we at once know the power to be forty diameters. Suppose, again, a power of one-fifth is being used, magnifying 125 diameters with bellows closed, and 275 with the same extended thirty inches; this gives a value of five diameters to each inch, and if the desired size is reached at twenty-five inches extension, we have a power employed of 250 diameters. By making these measurements (closed and open) for each objective habitually used, and recording the same in our note-book, an accurate and readily adjustable table of measurements is ready for all future work.
We now pass (thirdly) to the important subject of illumination, in many respects the most important in photo-micrographic work.
It goes without saying that to the favored few, whose time and means permit the harnessing of the sun's rays in their service, no artificial light can be produced which will quite take the place of the great luminary, but for the many, some other means must be sought.
When the promised days arrive that are to place in every man's house electric lights, cheaper than gas and as easily controlled, the problem will be satisfactorily solved; but at present we must content ourselves with prosaic kerosene, seeking only for the most practical method of utilizing its brilliant light.
After many experiments I have settled upon a flat, broad-based lamp of good oil-holding capacity, which is attached to a heavy retort stand with movable arm, enabling it to be carried to any desired height. A duplex burner and a tall chimney, producing perfectp232combustion, afford a light of thirty candle power, rendering possible the following average exposures with the plates I am now using, the variation in time being caused by differing densities and actinism of the tissues or substances to be photographed:
This lamp produces sufficient light for use with the highest powers, requiring the employment of a diaphragm to reduce its intensity. Too brilliant an illumination, flooding the field with diffusive rays, will almost certainly produce a blurred and indistinct image.
Microscope, camera and lamp being ready for use, it becomes necessary to provide a suitable support for each, in order to form a complete working outfit. Some writers have described and illustrated their apparatus as being carried upon two or more separate tables or trestles. This I have found to be a most objectionable method in our city houses, since the vibration produced by passing vehicles is unevenly communicated to camera and microscope, producing inevitably a disturbed or blurred image, especially when high powers are employed. By adopting, however, a long, solid platform, carrying all the separate parts of the apparatus, this objectionable feature is removed, any vibration is communicated to camera and microscope alike, and there is no blurring of the resulting image whatever. In my apparatus this platform is about five feet in length, with a raised portion at one end,p233upon which the camera is firmly clamped by a milled head operated from beneath. The cone front extends toward the platform, upon which the microscope (inclined horizontally) is secured at such a height that its tube precisely enters the middle of the cone. Thus, a straight line drawn from the object upon the stage through the microscope tube and camera should fall upon the centre of the focussing screen, and if all the parts are properly put together this will be the result, and the whole field will be equally illuminated when the lamp is placed in position.
The stand of the latter is not secured to the platform, but is left free to be moved about and placed nearer to or farther from the microscope, as may be found necessary to secure the best results. A bull's-eye condenser upon a movable stand placed between the lamp and the stage of the microscope, is necessary to concentrate the light upon the object, or upon the achromatic condenser when the latter is used and to aid in the equal illumination of the field. The latter is of great importance, since the result of an uneven illumination will be a negative of differing densities in different parts, marring its beauty, and at times rendering it utterly worthless. Too much stress cannot be placed upon the necessity of securing an even, brilliant light of proper intensity for the object under examination.
The arranging of the object in the centre of the field (under a low power) and the coarse adjustment of focus are done with the bellows tightly closed, which brings the focussing screen so near to the microscope that, whilst the operator sees the object thereon, his hand can readily reach the milled head, controlling thep234stage and other movements. But when the bellows is extended to the length affording the desired magnification it will be found that the object, whilst retaining its central position, has lost its sharpness, necessitating a final and careful focussing which is no longer possible in the same manner as before, since the ground glass and microscope are so widely separated that the one cannot be reached whilst looking into the others. Some special device becomes necessary in this emergency, and many have been made, mostly complicated and costly. The method I have adopted is the old and simple one of a fine cord passing around the periphery of the milled head controlling the fine adjustment, in a groove cut for that purpose, thence through a series of screw eyes to the rear of the frame-work carrying the bellows extension, where it is kept taut by a couple of small leaden weights.
The slightest tension upon this cord causes a corresponding movement of the fine adjustment, and nothing can exceed the delicacy of its working or its freedom from derangement. A fine fishing, line makes an admirable cord for this purpose.
Having sketched the various portions of the apparatus and brought the whole together into complete form, a few random extracts from my note-book may not prove uninteresting or valueless to some who are working in this direction.
Gelatine plates for photo-micrography. The requisites of a perfect plate are, great sensitiveness, combined with extreme latitude in time of exposure, and density in development. It should be of a fine texture, showing clearly the most delicate lines and markings,p235evenly coated and free from spots or blemishes of any sort.[2]