Chapter VIII: Introduction (6)

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.

PORCELAIN AND OPAL TRANSPARENCIES

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, [p217] either 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:

Saturated solution yellow prussiate of potash, 4 ounces.
Pyro 2 grains.
Ammonia (conc.) 2 drops.

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:

Saturated solution sal soda 5 minims.
Saturated solution potash 5 "
Saturated solution ferrocyanide of
potash 5 "
Bromide ammonium 1 grain.
Pyro 2 grains.
Water 4 ounces.

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. [p218] This 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 BY WET COLLODION. _From the Photographic Times._

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 by [p219] which 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.

[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 time [p223] at 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."

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 time [p224] he 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.

PHOTO MICROGRAPHY.

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, [p226] passing unnoticed the various stages by which its comparative perfection has been reached. Four essential parts make up the complete outfit.

A microscope with its object glasses and other accessories.

A camera with long extension bellows.

A lamp for illumination.

A solid platform to carry the entire apparatus.

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, [p227] the 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, the [p228] illumination 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.

THE CAMERA.

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 (6-1/2×8-1/2 inches) down to 3-1/4×4-1/4. The bellows are in three divisions, extending fully four feet, giving altogether nearly six feet from the microscopic stage [p229] to 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 side [p230] toward 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 6-1/2×8-1/2 inches, but by the employment of removeable rabbett kits, plates 5×7, 4×5 and 3-1/4×4-1/4 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 diameter [p231] to 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 perfect [p232] combustion, 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:

1-1/2 inch objective 3 to 5 seconds.
2/3 inch objective 7 to 90 "
4/10 inch objective 1/2 to 3 minutes.
1/5 inch objective 2 to 7 "
1/10 inch objective 4 to 10 "

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, [p233] upon 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 the [p234] stage 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, [p235] evenly coated and free from spots or blemishes of any sort.[2]

[2] The Stanley dry plate has all these qualities in the highest perfection.

It is most provoking to have an otherwise perfect negative marred or ruined by opaque or transparent spots appearing in its most important portions.

For development, ferrous oxalate or alkaline pyro are equally useful, and either may be employed, as suits the fancy or convenience of the operator. My own preference is for the latter, and I always use it with ammonia well restrained, having had no success with either soda or potash in this class of work. For all objects possessing much color it is best to continue the development until full density is obtained, but for very thin or transparent subjects, such as diatones or unstained vegetable tissues, it is far better to stop the development as soon as all details are out and resort to after-intensification, for which purpose bleaching with mercury followed by a ten per cent. bath of sulphite of soda will be found eminently satisfactory. I always use the alum bath, and invariably secure a clean negative of a cool gray color, resembling iron development.

Printing. The best ready sensitized paper can be depended on for producing satisfactory prints, showing the most delicate lines and markings of diatones and turning to any desired shade. Avoid over-printing, wash but slightly in two changes of water, the last slightly acidulated with acetic acid, and use an acetate of soda toning bath. Undesirable portions of the negative may be stopped out with a mat of suitable [p236] shape. Any ordinary cabinet card makes a neat mount of convenient size, upon which may be written the name of the object or specimen objective and magnification employed, and any other matter referring to print or negative which may be necessary to note.

A carefully kept note-book is a most important aid to the worker in photo-micrography, and it should contain all his failures and successes alike. Notes should be made of the specimen objective, magnification, exposure, plate and developer, which, carefully studied, will almost certainly enable him to secure a success with each exposure.

Lantern Slides.--It is well to make the negative as far as possible of a suitable size for producing the positive by contact printing, which is convenient and satisfactory, though there can be no doubt that reproduction in the camera affords better results. Slow gelatino bromide plates, such as Carbutt makes for this purpose, produce very satisfactory work, but the chlorides are so far superior that there can be little doubt of their being exclusively employed for positives in future. There is a richness of tone, combined with great transparency in the shadows and clear glass in the high lights, quite unattainable with bromide emulsions, and rivaling the best wet work.

* * * * *

Opaque Objects.--These may be photographed by the light from a lamp quite as well as transparent ones, through which the light is thrown, a matter of which I have thus far spoken only. A strong illumination must be obtained by the employment of a suitable bull's-eye condenser or a silvered reflector. The [p237] most satisfactory method, however, is by sunlight, allowing its direct rays to fall upon the object without the intervention of any condenser whatever. Very short exposures suffice with such illumination, varied only by the reflecting capacities of the object itself. A successfully exposed plate of this class of objects will give a print of the subject, standing out most brilliantly upon a black ground.

To secure the best results, most objects should be specially mounted for photographing. Some are best in a resinous medium, such as Canada Balsam, but most tissues are obscured or entirely obliterated in this medium. So far as possible all preparations should be mounted in a fluid of some description that will distinctly render visible many tissues and markings which would be lost in balsam. This subject, however, is one of so great extent that it would require a special paper, and I merely refer to it now because of its importance, hoping at some future time to enlarge more fully upon it.

You will notice that my remarks have been confined to work that may be done with objectives of low or moderately high powers, in no case exceeding one thousand diameters, having preferred to speak only of that which I have demonstrated by actual work as being practical. From recent experiments I am fully convinced that the lamp light, such as I have described, is capable of producing satisfaction, work with very much higher powers, and shall hope, at no distant day, to show prints made from magnification of not less than two thousand diameters, that will be satisfactory in all respects.

W. H. WAMSLEY.

[p238]

PRACTICAL SUGGESTIONS.

When preparing for an outing, consider the kind of work you intend to do and select your plates accordingly.[3] If it is intended to make instantaneous exposures, get the most sensitive plates possible; those of the highest sensitometer number should be procured. For subjects from still life, inanimate objects, landscapes, etc., etc., slower plates are preferable. When filling your holders, carefully brush all dust from the surface of the plates, ascertain that the lenses are clean, and wrap them in chamois. Carry no useless weight.

[3] The Stanley lightning is particularly recommended to amateurs for all quick work.

When you have selected your standpoint, plant the legs of the tripod well apart to insure steadiness of support and make sure that the camera is level and firmly screwed to the tripod. If you use a drop shutter, slow exposures may be made by holding the slide in the hand and passing it down slowly over the opening in front of the lens. When using double holders mark the side exposed as soon as made. Carry a piece of cetaceum paper, which may be used as a substitute in case you break your ground glass. The head cloth may be used as a changing box by covering the holder and box of plates with it and folding the ends around the wrists, securing them by rubber bands; then proceed by the sense of feeling. Before exposing draw the slides, so that no light may enter the plate holder.

Be sure you are right, then go ahead.

Before developing plates that have been exposed instantaneously, let them soak a few minutes in water [p239] with a small portion of soda or ammonia, then wash them and develop with the normal developer. Mr. Inglis suggests that for extra rapid exposures a very slow development with weak developer will give better detail and strength.

The paper films must be developed always with a strong developer to secure best results.

TRANSCRIBER'S ENDNOTE.

The headings in the Table of Contents do not necessarily correspond to headings in the text. A few examples will be mentioned. There is no heading for "PART I." in the text, though "PART II." is present. There are two headings "CAMERA BOXES" in the Table of Contents, but only one in the body. A second, matching one, has been added on page 110. The Table of Contents lists several types of pneumatic shutter for pp 124-129 that do not appear in the text under the same names.

In the Table of Contents, under the level-three heading "GELATINO EMULSION" at page 38, the two level-four headings "Preparation of Glass" and "Coating Glass" occur in the text under a level-three heading "DESCRIPTION OF APPARATUS USED IN MAKING AND WASHING EMULSIONS." on page 44, which corresponds to a level-three heading in the Table of Contents "APPARATUS USED IN MAKING EMULSIONS". This heading seems to refer to the same section of text as the level-four heading "Apparatus for Making" in the Table of Contents under page 38.

In the Table of Contents under heading at page 181, "How to Use the." was changed to "How to Use them." A few other such simple printing errors have been fixed silently.

Some captions of images or tables originally functioned in situ as section headings; some of these have roughly corresponding entries in the Table of Contents.

Originally, and in the html version of this ebook, section headings or captions of images or tables may also function in situ as part of the body text. In this text version, such captions and illustrations have been retained. However, any images that were originally embedded within paragraphs were moved out of paragraphs to between paragraphs, and if necessary, the caption was then duplicated in the text. Some illustrations that originally had no captions have been provided with captions labeled with "TN:".

In the table on page 43, showing the formulæ for gelatine emulsion, the fifth row duplicates the third row, probably erroneously.

The name "Ever" appears in the table of contents twice, in connection with Emulsions C and D, under the section starting at p 38. This name is spelled "Eder" on pp 43 and 44.