Fig. 1.Fig. 1.
Fig. 1.
While then it is not considered wise for the photographer to be his own retoucher any more than it is for every man to be his own lawyer or doctor, yet every photographer should know enough about the art and practice of retouching to appreciate good work and to detect the bad. And for that reason he should make a study of it both from the artistic and the mechanical points of view.
By such a course of study he will learn to produce that quality of negative that will require the least amount of improvement at the hands of the retoucher.p65
The work of retouching requires certain appliances to facilitate it, and its own special room or atelier. A small well-ventilated room having a window with a northern exposure is the best adapted for this work. This room should be supplied with the necessary conveniences, such as the retouching stand or frame, which in its earlier form is as represented in Fig 1, but which, after a time, became much improved upon; one form of improvement is shown in Fig. 2, but neither of these forms became universally used, as many artists fashioned their stands or frames to suit their individualp66taste or the requirements of their room or light. The march of improvement, however, is never delayed by such a condition of affairs, and was not in this case.
Fig. 2.Fig. 2.
Fig. 2.
Fig. 3Fig. 3.
Fig. 3.
It became necessary on the part of those interested in the manufacture of such apparatus to produce something that should meet all requirements, and this has indeed been accomplished by the production of the desk represented in Fig 3, which is called the Novel Retouching Desk and is suitable for any size of negative under 25×30; it has a false top which can be pulled down to darken the space in front of the ground glass cut out.
The bed on which the negative is laid can be set at any inclination to suit the convenience of the artist.
By means of the slide-rest the negative may be moved up or down to any desired position.
It is handsomely made in hard wood, and would be quite an ornament to any retoucher's room.p67
Next in importance would be a varnishing table, a small table or bench supplied with a gas or oil stove. See Figs. 4 and 5.
Fig. 4. Common Gas Stove.Fig. 4. Common Gas Stove.Fig. 5 Oil Stove.Fig. 5. Oil Stove.
Fig. 4. Common Gas Stove.Fig. 4. Common Gas Stove.
Fig. 4. Common Gas Stove.
Fig. 5 Oil Stove.Fig. 5. Oil Stove.
Fig. 5. Oil Stove.
Also Anthony's retouching varnish and varnish pot. See Fig 6, page 68.
A tin pot as shown in cut, with a filter and funnel in top; rubber stopper in spout.
The retoucher's room should also be supplied with
p68
The principal work of retouching, the stippling of the face, neck and shoulders when bare, and the hands, is done with Graphite or metallic leads, and directly upon the varnished or film surface.
Fig. 6. Peerless Varnish Pot and Filterer.Fig. 6. Peerless Varnish Pot and Filterer.
Fig. 6. Peerless Varnish Pot and Filterer.
The gelatine emulsion film is strong enough to take the pencil without varnish, and many prefer to retouch and even to print them before varnishing; but it is pretty generally conceded that gelatine negatives will receive the pencil better when varnished.p69
Before varnishing a gelatine plate, heat it as much as it will bear, so as to drive off all moisture from the film, then let it cool to the proper temperature before applying the varnish.
If the varnish used is too smooth or hard to take the pencil, a better tooth may be given it by the application delicately, to the parts to be retouched only, of a solution of rosin in turpentine, which should be allowed to stand and dry an hour or so before the retouching is done.
The work of retouching is very trying to the eyes; great pains should therefore be taken to ascertain the most favorable conditions of light and distance under which to work.
A negative should be kept at one angle and stationary while being retouched.
There should be as little lead used on a negative as is consistent with good work; make every touch tell to some purpose.
Note carefully the way the subject is lighted, and let the effect of the stippling be in that direction; you will thus be less likely to change the character or likeness of the face.
The lights and shadows should be caused to blend imperceptibly; this will give a harmonious effect.
Let the grain or stipple be seen in all parts suitable in fineness to the size of the head.
The refinements of negative retouching cannot be taught in books, although much has been written concerning the same.
Try to light your subject and develop your negative so as to get the utmost roundness or relief; then be careful not to destroy this modeling, but improvep70it by retouching, only doing so much work as to give a soft, clean-looking complexion.
Patient perseverance, close observation and trying again, will bring a certain degree of success, and while only the few can become first-class retouchers all may learn to improve their work by this great help to photography.
It was long ago said that silver printing was doomed, that in a few more years it would be among the things that were.
Other processes have been introduced, have had their little day and have passed off, some of them of much merit, and, it was supposed, possessed of every element of permanency, but they were found wanting in some very important respect, and so not being able to hold their ground they passed into the limbo of neglected things.
Silver printing, however, still maintains the field against all comers, and does so by its intrinsic merits alone. No other process has equalled it in ease of production and in beauty of finish, and it is doubtful if any process has results of greater permanence, taking the best products of the process as samples.
The one defect of the process is the possibility of its products fading, but we must not judge of a process by its poorest examples, but rather by its best; if such should be the decision, there are at this day thousands of silver prints that are co-existent with the process and remain as perfect as it is possible for anything on paper to be after such a lapse of time.
A process that is so simple and easy that it can bep71acquired in a few hours, is predestined to careless working, slovenly manipulation, and to endless scamping at the hands of careless workers. What wonder then if prints fade which were only half made.
Suffice it that the process, intelligently and conscientiously worked, would never suffer from such an imputation.
All professional photographers practice the silver printing process with more or less of success, as they bestow care and intelligence in the working and are zealous for the reputation of their work.
The proper handling of a negative by the printer requires as much study and skill on his part as does the posing and lighting of the subject in the studio; and the printing room should be as replete with every convenience for forwarding and improving the operations therein conducted, as any other department of the establishment.
This room is generally situated at the top of the house, and wherever situated, should be so arranged that the east, south and west sides may be opened to the sun, that his direct rays may be utilized from the earliest to the latest working hours. Part of the room should be partitioned off in such a manner, and illuminated in such a moderate degree, that the sensitized paper may not suffer from excess of light while the frames are being filled and the changes made.
The printing room outfit consists of the various sizes of printing frames, cardboard, tissue paper and cotton-wool for vignetting, and knives, long-blade scissors, and glass forms for cutting the paper to various sizes,p72light tight drawers to hold the prepared paper, shelves, and racks for the negatives.
The silvering room may be also used for other manipulations in the process, such as fuming the paper and washing the prints, and should be furnished with all the conveniences for such work, which consist of
A plain silver solution, of a strength of 30 grains of nitrate of silver to the ounce of water in hot weather, increasing to 60 grains in the coldest, with enough bi-carbonate of soda added from time to time to keep a small sediment of carbonate of silver in the bottom ofp73the bottle or dish, is all that can be desired as a silvering solution for albumen paper. It only needs to be kept up to the proper strength by the addition of silver nitrate and water, when required; and when it shows signs of discoloration a little more soda and an hour's sunlight will keep it in good order the year round.
Albumen paper is sensitized by being floated for a time on the surface of this silver solution, albumen side down. For this purpose it is necessary that the solution should be held in a flat dish, like a tray, with sides from 1½ to 2 inches high, and of a size suitable to the size of the sheet of paper to be floated; if a full sheet, then the dish should be 19×24, and may be of porcelain, agate ware, hard rubber, or any other kind that will resist the corrosive action of the silver solution.
Pour the silver solution into the dish; there should be enough to give a depth of at least half an inch. If there is any scum or dust on the surface after the air bubbles have subsided, take a long strip of tissue paper and draw the edge over the surface of the solution, which will remove the scum or any floating dust or air bells that may remain.
Place your paper on a bench or table, albumen up, and with a large tuft of cotton rub the surface, using a light friction over the whole; then turn the sheet of paper over and take between the thumb and first finger of each hand opposite corners diagonally across the paper, holding the corners up and near together; let the sag of the paper sink one end first, until it touches the solution, which can be plainly seen; then let the hands fall until the other end has reached thep74surface of the silver; then lower the corners gradually, until the paper lies flat on the solution, care being taken that none of the silver solution runs over the edge of the paper to the back.
The corners of the paper may now be gently raised to see if any air bubbles have attached themselves to the surface of the paper; if so, remove them and let the paper fall again to the solution. It will now be seen that the edges of the sides of the paper will begin to curl back, as if repelled from the solution. This may be permitted to a certain extent, but not so far as that the wet surface shall curl over against the back of the sheet. After a short time this action ceases and the rolled edges unroll and fall again upon the solution, which, when they have reached and lie flat, may be taken as an indication that the paper is sufficiently silvered, when it should be removed. With a small pointed stick raise the left corner farthest from you from the solution, take it between the thumb and first finger of the left hand and raise it very slowly, until the right hand far corner is off the solution. Take that corner between the right hand thumb and finger and continue to raise the paper, still very slowly, until it is clear of the solution; then hang it up to dry in a moderately dark place, or better still, place it face down, on a sheet of clean blotting paper, put another sheet over it and on that the next sheet that is silvered, and so on alternate sheets, until you have floated as many sheets as may be needed.
When this is done turn the papers over, bringing the sheet first silvered to the top, which on removing the blotting paper will be found surface dry at least, and may now be completely dried by artificial heat, or byp75hanging it up two sheets together, back to back, on lines with spring clips, until they dry spontaneously, when they are ready to be fumed.
The fuming box is usually a light-tight box with two compartments; the upper part has a door and should be sufficiently large to hold the amount of paper necessary for a full day's work, without crowding the sheets together or preventing a free circulation of the fumes between their surfaces.
The paper is taken from the lines, each two sheets back to back, the corners fastened with clips and set up on end in this compartment or hung on lines, as the case may be. When all the paper is in, shut and fasten the door and into the bottom compartment (which is usually a shallow drawer, and separated from the upper only by a lattice work of wood) place a saucer containing an ounce or two of strong liquor of ammonia, push the drawer in, thus closing the compartment, and leave for fifteen or twenty minutes, or until you are ready to use the paper.
When you remove the paper from the fuming box do not expose it to strong light until you have it in the printing frames, nor after that, until you have toned and fixed it. Take the spent ammonia from the box and pour it into a bottle; it is useful for other purposes. Many printers cut the paper to size before printing, others simply tear each sheet into halves, quarters, eighths or twelfths, and print them thus, trimming them afterwards, some before toning, others after they are finished and before wetting them for mounting. The most economical method is to trim before printing;p76all the trimmings should be carefully saved for the silver they contain.
A toning solution is composed of chloride of gold in water with enough carbonate of soda to make it slightly alkaline, and a pinch of common salt. The action of toning is merely the deposition upon the metallic silver in the print of a certain minute quantity of metallic gold from the solution, which deposit causes the change of color that may be seen while the toning is taking place.
The normal toning solution is varied endlessly by the addition of acetates, chlorides and nitrates of various metals and salts and of borax and chalk and such, the object being to produce unusual tones, such as sepia, blue, blue-grey, brown and black, but the richest and most agreeable tones may be produced as well by the simplest means.
Into this put half as many grains of pure chloride of gold as you have sheets of paper to tone; after adding the gold make the solution alkaline by adding enough of a strong solution of a carbonate or bicarbonate of soda to turn red litmus paper just blue; then add a pinch of salt, and the toning solution is ready for use. When half your prints are toned, or the toning proceeds too slowly, add more gold, allowing not over 1 grain of gold for each sheet of paper. When all the prints are toned, put the toning solution into a bottle to keep for the next time, when it will probably work better than at first;p77use it until it becomes badly discolored, then put it into a large bottle to save the waste gold.
The toning must be done in a flat dish that is as large as the largest print that requires to be toned.
Your toning solution being ready, the prints are now to be prepared for toning by being deprived of all excess of silver and free chloride not acted on by the light; in order to do this, put them one by one in a large dish full of water, in this dish keep them in motion for some little time, then prepare another dish containing the same amount of water slightly acidified with acetic acid, and remove the prints into this one by one as before, keeping them in motion; they will at once commence to turn red, and when they are so they may be taken out, the waters of these two washings must be saved for the silver contained therein.
The prints require two more waters after the acid, when they are ready for toning.
Immerse half a dozen or more of the prints, one at a time, in the toning solution and watch the change of color.
They may at first become a little redder from the action of the salt in the solution, but they will soon change to a brown and then to a bluish or grey brown. And when the faces have become as clear and white as to suit as finished pictures, remove them to fresh water and proceed with another batch until all are done.
Hyposulphite of soda, about 1 lb. to a gallon of water, constitutes the fixing solution; its function is to dissolve all the chloride of silver that may remain in the prints after their previous washing and toning.p78
The prints should be immersed one at a time, and kept in motion so that the solution may have an equal action. When there are a large number of prints the dish containing the fixing solution should be correspondingly large, so that the prints may not be massed together but kept separate and free for the more perfect action of the fixing solution; they should be kept in motion until the fixing is completed, which will be in about 15 or 20 minutes. Some printers ascertain that the action is complete by holding the print up and examining it by transmitted light; if it looks mottled and uneven it is not fixed, but if you can see the fibre of the paper and all is clear, then remove the prints from the hypo into a dish containing brine or common salt and water, one by one as before, and keep them in motion in this brine until all are well saturated with it; then let fresh water run into the dish, which will gradually change the brine to clear water.
The prints are put into the brine, and this gradually changed to clear water to prevent blisters or a separation of the albumen from the paper in the form of blisters. The water may be allowed to run into the dish, the prints being kept in motion, and in the course of an hour they will be sufficiently washed; they may then be taken out and placed between the sheets of blotting paper to remain until next morning, when they can be overlooked, the blemished prints thrown out, and the perfect may be mounted.
The fixing solution should not be used a second time, but should be thrown into a large barrel with the washings, that at some future time the silver may be recovered; when the barrel becomes full, a small amount of saturated solution of protosulphite of ironp79may be thrown in, the water stirred well, and when the sediment has settled to the bottom the clear liquid may be drawn off and the barrel is ready to receive the next washings of hypo.
The selected prints are again placed in water and permitted to remain until they become saturated; in the meantime some starch paste should be prepared. The prints are then removed from the water and placed on a sheet of glass, face down; when all are thus placed, squeeze out all the water and they are ready to mount. Now with a wide bristle brush spread the paste evenly on the back of the print, carefully removing any lumps or dust or fibre of any kind, then insert under the edge of the print the point of a knife-blade, raise it until you can take it in the fingers, then place it pasted side down on the face of your mount, adjust it evenly and lay it on the table; now cover it with a piece of clean white paper, and with the palm of the hand rub it down until all parts are in contact and all air is expelled from between the print and mount. As the prints are mounted they should be placed in rows on clean white or blotting paper, one layer over the other; on the top place a clean sheet of paper and over that a board of the proper size with a weight on it to press the mounted picture flat; in the course of an hour they will be dry enough to spot.
With a fine pencil brush and Indian ink, go over the prints and carefully touch up all the white spots and other blemishes that may be found on the surface, so that they harmonize in color with the surroundingp80parts. When this is done the pictures may be lubricated for burnishing.
Make a pad of Canton flannel, get a piece of white castile soap, rub the pad on the soap until it is well covered, then with this soaped pad rub the surface of each print separately, carefully covering every part of the surface; keep the pad well soaped by rubbing it on the soap after every 2 or 3 prints. While this is being done the burnisher may be heated; when the tool is hot enough to hiss when touched by a wet finger, proceed to burnish. Do not use much pressure; too great pressure will degrade the whites of the picture.
When they are all burnished go over them again with a moderately soft lead pencil, touching up and blending any streaks or spots that may be found; if any streaks or dirty lines are discovered in the direction of the draw of the burnisher, they may be removed by light friction with a piece of Canton flannel moistened with alcohol. This completes the photograph.
Mr. Ernest Lacan, a prominent artist of Paris, France, about ten years ago, wrote for thePhiladelphia Photographeran account of some of the prominent studios of that great city, from which I take a description of the studio and establishment of the celebrated Reutlinger.
This establishment comprises the fifth and sixth stories of a fine house on the Boulevard Montmartre.
A handsome and wide stairway leads to the studio. The first thing that strikes you on entering the ante-chamber,p81which is transformed into an office, is the lowness of the ceiling and the want of light. On the right is a room, larger and better lighted, for the sale of choice specimens of his work. On the left are the exhibition and waiting rooms, which are of medium size and whose principal ornaments are the framed pictures, which cover the walls. A small door leads to the skylight, of which the diagram at the head of this article is a correct view as taken from a photograph.
THE PHOTOGRAPHIC STUDIO.THE PHOTOGRAPHIC STUDIO.
THE PHOTOGRAPHIC STUDIO.
The view is taken from the door at which you enter. This gallery is formed of two mansards, which have been united by removing the partition; is 39 feetp82long by 13 in breadth; its height to the top of the upper sash is about 16 feet; the light comes from the north. It is by means of an ingenious combination of white and blue shades, that the artist succeeds in obtaining the charming effects so much admired in his productions. At the end of the gallery is a small room for ladies. The door which is seen on the left leads to the laboratory, which is divided into three small apartments. The first is used for cleaning plates, the second for their preparation, and the third for developing negatives.
TN: Diagram of Loescher & Petsch
This is a diagram of the studio of the famousp83Loescher & Petsch, of Berlin, who became so well known, some years ago, through the style of picture called "Berlin Heads," which were among the first samples of fine photographs from retouched negatives brought to this country, and which certainly created a sensation.
FIG. 1.FIG. 1.
FIG. 1.
The shades are arranged so as to show how some of the most charming effects of illumination are produced. The room is filled with diffused light, with a ray of direct light falling so as to produce a clear high light on the prominences of the head of the sitter.
The next diagram is one of the Biglow studios. Mr. Biglow is the author of a book on lighting and posing, which had a large sale, and is a valuable book for positionists.
These three views represent forms of skylight and side-light with north exposure, by which all the finest effects possible are obtained, but other forms of exposure are capable of being utilized with fine success.
The studio of Sarony, of New York, is lighted with a top light similar to the top light of the Biglow studio, and without any side light at all.
A prominent artist of Brooklyn produces very finep84work under an east light, or rather a light a little south of east, which to the ordinary photographer would be considered a very difficult light to work. Good effects can be produced, however, under any form of light by the use of shades, screens and reflectors, so that no photographer need regret a favorable location, because unable to have a northern exposure for his light.
The studio should be furnished with every requisite for the production of the finest work, such as
All these things are of importance, but should be used with taste and judgment. The photograph should never be a picture of a piece of furniture, with a figure thrown in, but rather the accessories should be used only to improve the figure and make it more prominent by increasing the perspective, when possible or allowable.
A solar beam of light is a bundle of rays; a ray being the smallest portion of light which can emanate from a luminous body.
Each of these rays possesses distinctive characters, both as regards their chemical functions and colors.
Sir Isaac Newton proved that the white light emittedp85by the sun is not so simple as it appears, but is composed of vivid colors, as shown by his beautiful experiment, the Analysis of Light, which is exemplified by the use of a glass prism. (See fig. 1.)
FIG. 1.FIG. 1.
FIG. 1.
The ray of light A, E, being admitted into a darkened room through a hole A, in the shutter, would fall upon the wall at E. As soon as the prism, B, C, is placed in the path of the sunbeam so as to allow it to fall on one of its angles B, the ray will be refracted, or bent out of its course so as to pass through the prism (as in the line D) and not in the same line, A, E, that it would have done had the prism not been interposed.
Another effect also takes place; the ray of white light is decomposed into its component colors, and if you stand at a short distance from the prism, you will see that these colors are spread out in a triangular form, the base of which is on the wall and the apex at the angle C of the prism. Remove the prism and it is seen that the splendid display of colors upon the wall has disappeared, and a round spot of white light, E, is seen below the place occupied by the spectrum.
The colored image on the wall is called the prismatic or solar spectrum, which, according to Sir Isaac Newton, is composed of seven different colors. The color at the lowest portion of the image is red and the one at the other end is violet, the intermediate parts being occupied by five other colors, and the whole arrangedp86according to the table below, the proportion of each color having been measured by Fraunhofer with the greatest care, with the results placed opposite to each, corresponding with the 360 degrees of a circle, the red ray being the least and the violet the most refracted of this chromatic image.
The sunbeam, the ray of white light, contains powers within it of which the earlier philosophers had but a faint idea, besides its accompanying heat. There is a principle associated intimately with it, which has the power of decomposing and of determining the decomposition of chemical compounds.
This principle is "Actinism" and is as perfectly distinct in the nature of its properties from light, as light is from the principle of heat, with which it is also closely connected.
Actinism may then be considered as the fundamental principle, on which photography is based, and its power is exerted in forming the image on the sensitized plate in the Camera, as well as subsequently in forming or causing the impression on the sensitized paper exposed to the light beneath the negative.
In this connection we have only to consider thep87application of this Actinism through the medium of a combination of lenses to form an image on a sensitized plate in the Camera.
It has been shown that when light passes through a prism of glass its colors are separated; this separation is caused by the unequal refrangibility of the different colored rays, the violet being the most and the red the least refrangible of the seven rays.
A ray of light passing through a vacuum progresses in a perfectly straight line, but all matter, however attenuated it may be, has the property of refracting or bending the ray of light.
The refractive power of some substances is immense, while that of others is very trifling. The mode of the refraction depends on the comparative density or rarity of the respective media. If the medium which the rays enter be denser, they move through it in a direction nearer to the perpendicular drawn to its surface; on the contrary, when light passes out of a denser into a rarer medium, it moves in a direction farther from the perpendicular. This refraction is greater or less, that is the rays are more or less bent or turned from their straight course, as the second medium through which they pass is more or less dense than the first.
We next study the utilization of this power of refraction in the manufacture of lenses to overcome the unequal refrangibility of the colored rays of light.
A lens for use in photography is made of glass as pure and as colorless as can be procured, and is ground into such a form as to collect or disperse the rays of light which pass through it. Lenses are of different shapes, and thence receive different names.p88
FIG. 2 E. 1. Double convex. 2. Plano-convex. 3. Concavo-convex. 4. Double concave. 5. Plano-concave. 6. Meniscus.FIG. 2 E.1. Double convex. 2. Plano-convex. 3. Concavo-convex.4. Double concave. 5. Plano-concave. 6. Meniscus.
FIG. 2 E.1. Double convex. 2. Plano-convex. 3. Concavo-convex.4. Double concave. 5. Plano-concave. 6. Meniscus.
The figures 1 to 6 represent sections of the variously shaped lenses which are combined for use in photography.
The design in forming lenses is to procure a medium through which the rays of light from any object may pass and converge to a corresponding point beyond; the manner in which the rays proceed through the lens, and then centre in a focal point, will depend on the form of the lens, its capacity for refraction and the distance of the object.
The double convex lens may be viewed as a portion cut out of the side of a sphere. Here, as in all cases of convexity, the focus of the parallel rays passing through the lens is at the centre of the sphere. (See fig. 3.)
FIG. 3.FIG. 3.
FIG. 3.
A plano-convex has only half of the refractive power of the double convex; the parallel rays, falling on the convex side of the lens, would converge at the distance of the whole diameter of the sphere. Thus the focal point at which the rays of light converge is always regulated by the degree of curvature of the lens. Thus the double convex lens has the greatest power of converging the rays of light; the plano-convex has only half the power of the former. Both these lenses have also the powerp89of magnifying the image of an object seen through them in the same proportion.
The double concave and the plano-concave have the power of dispersing the rays of light and of diminishing the image of an object seen through them in the same proportion.
FIG. 4.FIG. 4.
FIG. 4.
The meniscus lens has but a very slightly dispersive power, and the concavo-convex merely separates the parallel rays to the thickness of the lens and sends them on parallel as they entered.
All these lenses, having something of the prism in their shape, have the power to a greater or lesser extent of decomposing the light that passes through them. This is called chromatic aberration, because the colored rays do not all converge to the same focus; thus the image seen through them is surrounded by a fringe or border of color.
Single lenses lack the power of producing a straight image of a straight object; the image will have the curve of the lens through which the light passes to form it; a double convex lens will give a greater curve than a plano-convex. This is called spherical aberration.
The main object to be considered in the manufacture of a lens for photographic purposes is to produce one with the least spherical and chromatic aberration.
Spherical aberration is overcome to a great extent by the use (in connection with the double convex) of a meniscus lens.
Chromatic aberration is overcome by the use of two glasses of unequal density in forming one lens; thusp90the front lens of the portrait combination is composed of a double convex of crown glass and plano-concave or meniscus of flint glass, which two glasses are sealed together with Canada balsam.
The forms of lenses which are corrected for chromatic and spherical aberration will be seen in Fig. 5.
FIG. 5.FIG. 5.
FIG. 5.
These lenses are termed achromatic, and, although each is formed of two kinds of glass, they are sealed together so as to be practically one lens.
Every manufacturer of portrait or view lenses, uses the six forms shown in the diagram (Fig. 2), in some manner peculiar to himself, but of the six, four will be found in every combination in general use, varied in radii, construction and dimension, according to the use for which they are intended.
Formerly the photographer's choice of lenses was restricted to two combinations, the double combination for portraits and the single for views. There have of late years been invented a great variety of lenses, among which and in the order of invention, probably are Petzval's Orthoscopic, Harrison's Globe, Ross's Doublet, Darlot's Wide Angle and Rectilinear Hemispherical, Steinheil's Aplanatic, Voightlander's Euryscope,p91and greatest of all, Dallmeyer's Patent Portrait,Wide AngleandRapid Rectilinear Lenses.
The combinations of lenses are three, the single, double and triple; the latter is now no longer in use, or if so, its use is greatly restricted. The single combinations have greater focal length than the double, and consequently at the same diameters larger pictures are obtainable, and they are principally used for landscape or view work.
The double combinations, so called from having a second pair of lenses behind the first, which have the effect of shortening the focus about one-half, whereby the action of the light is accelerated, and both the spherical and chromatic aberrations more perfectly corrected, which result in an image more delicate in definition and more rotund in form, thus peculiarly qualifying them as portrait lenses.
In the selection of lenses for studio or view work, the intending purchaser, if desirous and pecuniarily able to avail himself of the best, will naturally inquire what make of lenses is the most widely known and used, and it will not take much time to procure a satisfactory answer to the question.
It has been conceded now for some years, both in Europe and in America, that the lenses manufactured by J. H. Dallmeyer, of London, England, are superior to all others, not only for their fitness for the work for which they are specially constructed, but for their adaptability to work beyond anything claimed for them by the maker, and also for a certain undefinable and æsthetic quality inherent in the negative made by these lenses.
The fact that there is not in the wide world a photographicp92establishment of any note that does not possess one or more of these lenses is strong evidence of their superiority. In the quality of the glass used, in the perfection of finish and adjustment, in softness, crispness and depth, in rapidity, illumination and every quality that recommends a lens, the Dallmeyer lenses are unrivalled.
FIG. 6.FIG. 6.
FIG. 6.
The portrait combination now in general use, was first constructed from calculations made by Professor Petzval, of Vienna. Its optical components are, a front crown lens of unequal convex curves to which is cemented a double flint lens of unequal concave curves. The back combination is a crown lens of unequal convex curves and a concavo-convex flint lens at a little space from it. (See Fig. 6.)
For more than a quarter of a century this form of lens had been used without material change in its construction, until Mr. Thos. Ross, by a modification of the curves, succeeded in flattening the field and increased its rapidity by shortening the focus, but left it with the peculiar shallowness of focal depth, especially in the larger sizes, which has been the torment of photographers to this time.
Mr. Dallmeyer was the first to improve upon thep93original portrait combination, and in his new Patent Portrait Lens he has most ingeniously obtained a diffusion of focus at the will of the operator. By a quarter or half turn of the cell of the back combination the focus is diffused, giving an agreeable softness in place of the shallow plane of excessive and wiry definition so familiar to the photographer.
Fig. 7.Fig. 7.
Fig. 7.
The diagram, Fig. 7, shows a section of Mr. Dallmeyer's New Portrait Lens. There are two actinic combinations, of which the front resembles the Petzval lens; the back combination differs as regards the ratio of radii of the lenses used, the crown being a deep meniscus and the flint a deep concavo-convex, with their adjacent surfaces dissimilar; their positions also are reversed, the concavo-convex of flint occupies the external position, instead of as in the Petzval, and this lens being mounted in a cell capable of being unscrewed supplies the means of regulating the spherical aberration of the system at will. The lower portion of the diagramp94exhibits a plan of the mount of the back flint glass lens; this cell admits of being unscrewed, one or more parts of revolutions of the screw indicated by an index and divisions; with this back lens screwed home this combination has all the good qualities of the old form of portrait lens, but with a flatter field and wider illumination.
There are three distinct classes of portrait lenses. The first are lenses of large diameter and aperture compared with their short focal length. In this class the greatest rapidity is obtained at the sacrifice of flatness of field. Of this class are the B and C lenses of Dallmeyer.
The second class are lenses of equal diameter and aperture with those just described; but with about double their focal length, and therefore less rapid, but with more field and wider illumination; of this class are the A series.
In the third class are long focus lenses, which, at three inches diameter have fifteen inches focal length; with the result of a larger and flatter field; they are, however, necessarily slow, but well calculated for out-door views, groups and copying. Of this class are the D series, which, since the introduction of the rapid dry plate, have become available for ordinary portrait work in the studio.