Part 10

Any of the above developers will be found to rapidly bring out all there is in the plate, and if over-exposure is feared, they may all with advantage be diluted, with an equal quantity of water, in order to slow down their action.

In another dish, it is advisable to have the following _re-developer_, to impart density to the plates, as they become ready for that operation, or to successfully deal with any, which are found to have been considerably over-exposed, and upon which, the first developer is acting too vigorously.

RE-DEVELOPER. NO. 1. Hydroquinone 1/4 ounce Sodium sulphite 2 " Potassium bromide 1/4 " Boiling water 12 "

NO. 2. Washing soda 2 ounces Sodium sulphite 2 " Water to make 12 " For use mix equal quantities.

By employing two different developers in the manner suggested, it becomes a simple matter to produce good negatives, from plates having had all kinds of exposures, some under, some over, and it may be some which have had about the right exposure; in this way one of the most fruitful causes of failure in the production of hand-camera pictures, _error in exposure and development_, is minimized, if not altogether done away with.

There are sometimes occasions when out with a hand camera, when subjects present themselves, offering exceedingly good opportunities for securing pleasing little pictures, but which require one, or two seconds' exposure, to render them successfully. At such times it may generally be arranged to rest the camera on a stone, wall, or gate, or to hold it pressed against a tree, or some other rigid support. As an example, the illustration of a woodside with birch trees, facing page 136, may be pointed to. In this instance, when out cycling, the place and lighting on the tree trunks, struck us as pleasing, and worth trying to secure a record of, even though but a hand camera was being carried at the time.

Having dismounted, and found a point from where it might be attempted, and where conveniently grew a single tree, the lens was opened to (if recollection does not deceive) _f_/11. Then the camera jammed close to the tree trunk, and two seconds' exposure given, taking especial care that no movement took place.

The plate being in due time carefully developed, and as far as possible contrasts kept down, the result proved satisfactory enough.

It could more conveniently have been photographed, of course, if a camera and tripod had been available, but it is one of many such instances, where, when shutter exposures only had been prepared for, occasions arose, demanding longer exposures than were possible, unless, some such temporary support be pressed into use, as in this instance.

For successful work, see that the camera is simple, its parts, of the best your pocket can afford. Give the slowest exposures your subject will allow. Develop for softly modelled negatives first, getting what density is required afterwards. See that the camera is held perfectly steady, during exposure, and don't forget it is simply a camera, and lens, and will require _you behind it_, just the same as any other employed with a tripod, and in conclusion bear always in mind, _it is the simplest form of camera work and the most difficult_, making the utmost demands on your skill, if high-class results are to be the outcome of its use.

_W. Thomas._

_Lantern Slides._

A lantern Slide is a transparent positive on glass or other transparent support, usually 3-1/4 inches square, and is placed in the lantern in such a way that by suitable illumination and optical arrangements the image on the slide is made to intercept some of the light given off by the illuminant from a screen, which without the screen would be wholly and evenly illuminated by the light.

In viewing a paper print we are really observing the paper by reflected light, part of our view being intercepted by the image formed of pigment or reduced metal; the amount of light not being very great a very thin layer of pigment is required to produce the appearance of a sufficiently robust image. If the image alone or with its vehicle be stripped from a good print on paper this image viewed by transmitted light will be found to be extremely faint, far too faint to be of any use as a "transparency," and also too thin to be of any use as a lantern slide. On the other hand, what we know as a "transparency," such as is often used for window decoration, backed, perhaps, with ground glass, would be found much too dense or robust for use as a lantern slide. In density, then, a "slide," as it shall hereafter be called, comes between the image on a paper print and that on a "transparency." In "gradation," or gamut of tones, the slide ought to be superior to either the paper print with its almost absolute clearness over large areas, or the transparency with its dense shadows and its comparatively heavy lights. In fact, in a good slide we have every grade of deposit from perfect transparency to nearly complete opacity. But the extremes must be very sparingly present, and the transition from one tone to another must be gradual, all intermediate notes between highest and lowest should be represented.

Other qualities go to make the perfect slide; the metallic or other deposit forming the image must be in the utmost degree fine, no approach to "grain" must be perceptible even under the highest magnification. The colour, or "tone," must be not only pleasant but appropriate.

The loss of light in its journey from the illuminant to our eyes is enormous; the disc on the screen is simply a greatly magnified image of the light, and here is great loss; add to this the interception of some light by the opacity of the slide, and the fact that much more is lost in reflection from the screen, and absorption by the screen, and it is easy to realize that the image from the screen reaching our eyes is vastly less bright than that reaching the eye when, for instance, we examine a slide in the hand by transmitted light. And loss of light means increase of contrast, so that a slide which would seem about right in gradation in the hand would be altogether soot-and-chalk as a screen-image. So too if we have in the slide already shut out much light, by making the slide foggy, or over dense, it is easy to see that when the image reaches our eyes from the screen this vicious opacity will be immensely increased in its mischievous properties. The first style of slide gives screen-images sometimes called "midsummer snow-scenes"; the other slide is simply called "foggy." Both must be assiduously avoided.

It need hardly be said that the plates prepared by some processes are more likely to yield good slides, such as are described above, than plates prepared by other processes; no one process can claim to possess in itself superiority in all respects. Collodion, for instance, is less apt to give foggy slides, and it is easier to intensify than gelatine, but it is also more prone to give "hard" images. Collodion is at its finest in the form of collodio-bromide emulsion, which gives slides remarkable for fineness of grain, for clearness, and for richness of tones; but when we have to copy in the camera, the operation with collodion emulsion is protracted, unless we have bright daylight or a condensing arrangement, which with large negatives is often out of the question. On the whole it may be taken that gelatine-bromide emulsion is the process to be recommended, not only on account of its convenience and celerity, but in view of the many inherent points of excellence that it possesses. In any case, want of space will cause us to confine attention here to that process, and any one mastering the use of gelatine-bromide slide-plates will have nothing to fear from competition with other processes in all-round work. The writer has a leaning towards slide-plates as slow as he can procure them, because slowness almost always goes hand in hand with fineness of grain and freedom from fog.

There is one point of importance that should be noted in working with gelatine for this purpose. Distilled water should be used if possible for all solutions. Tap water--especially hard water--is apt to produce with the gelatine a certain amount of scum which, if present in any appreciable degree, cannot fail to affect the quality of the slides; but treatment with an acid alum bath as described later has a very salutary effect in removing any scum that may have formed during the "liquid" operations.

In the mechanics of making a slide from a negative we have only two methods to consider. If the slide-image is to be the same size as the negative, or a part of the negative, we print by _contact_, that is, we put the negative and the slide-plate face to face in contact, and we expose to light, the negative being next to the light; this corresponds with making a print on paper. But when we desire to make a slide including all the subject of a negative larger than a slide-plate, or, in fact, when we desire to alter the size of the image at all, we copy the negative "in the camera." The simplest method of doing this is to fix up the negative so that it is evenly lighted and make a photograph of it in a camera; but the adjustments necessary for such an operation would be found awkward, and so a "reducing camera" of some kind is generally used. Many such cameras are on the market, and consist of devices for holding the negative in a suitable position with regard to a small camera furnished with a lens and a dark slide holding a lantern plate. Either the negative-holder or the camera should have possible movement in all directions vertical to the optical axis of the whole, and in addition it is often desirable to have a certain amount of movement in other planes, in order to correct certain optical defects that are sometimes found in negatives. The writer has for many years used a small camera with its front stuck into the front of a large camera, one or other of these cameras has every necessary movement. The device is figured here.

Whatever arrangement is used the end of the apparatus bearing the negative is directed towards a good and even light; and it is well to place about two inches in front of the negative towards the light a piece of finely ground glass for ordinary negatives; this glass is with advantage omitted with extra dense negatives.

It goes without saying that the exposure, whether we are working by contact or in the camera is of the utmost importance; but it is not possible in an article such as this to give even an approximate idea of the exposure suitable under any concatenation of conditions. The best clue to exposure is to be found in development, and in results. It is necessary to know what happens after normal exposure with a given developer, and then if any variation is noticed to alter the exposure. If a plate develops more rapidly than the normal, it may fairly be deduced that the exposure has been too long; but if we are dealing with a specially contrasted negative it is better so. On the other hand, when we are dealing with a thin negative, especially if the scale of gradation is short, we require an exposure less than what would under normal conditions lead to complete development in the normal time. And again some plates require to be developed to a greater point of apparent density than others; this is a matter of experience. Briefly put, there is no royal road to good slide-making, experience is necessary.

In actually making the exposures certain points must be kept in mind. If we are copying in the camera with daylight as illuminant it is very important to use the light from the north; if we use other light we shall be much put out on most occasions by awkward variations of the brightness. A very large number of operations are rendered nugatory by carelessness in this matter. Even the most experienced worker will find it impossible to expose plates with anything like accuracy when he has to deal with direct sunshine at one time, thin white clouds at another, and dark clouds at a third. And in making exposures by contact the beginner must be fairly accurate in judging the time of exposure and the distance from the radiant. A good plan is to tie to the gas jet a piece of cord having knots at convenient intervals, such as at 9, 12, 18 and 24 inches, and in making an exposure to use these knots as guides to the distance; moreover, the law of "squares of distance" must be remembered; the intensity of light varies inversely as the square of distance from radiant to receiver, provided, of course, no optical arrangement is introduced to modify the path of the rays. Consequently, for example, if ten seconds is found to be a proper exposure at nine inches from the light, the corresponding exposure at eighteen inches will not be twenty, but forty seconds (9^2=81. 18^2=324). And as it is sometimes awkward to hold the frame and attend to a watch at the same time, a metronome, ticking seconds, will be found convenient, or a clock with a second hand may be placed where it can be seen during the exposure. A landscape slide without clouds, if the horizon is in the picture, is usually considered a failure, and has been dubbed "bald-headed." Really good workers often put clouds into slides by "combination printing," which in some cases is comparatively easy, in others very difficult. If we are working by reduction from a good-sized negative, with a fairly even horizon, the difficulty is not great. The landscape part of the negative is first exposed, the sky being masked if necessary, and a cloud negative is then substituted for the landscape negative, a part of the former being masked to correspond with the landscape on the latter, and a second exposure is made on the same slide-plate. Admittedly in all cases this requires "some doing," in many cases it is extremely difficult. An easier, if less "sportsmanlike," method is to make the cloud slide on a separate slide-plate, and to use the latter as a "cover-glass" for the slide. The cloud may cover the whole of the second slide, and that part of it not required may be wiped out by means of a reducing solution, used with a brush, such as the ferricyanide and hypo one described later. This method will be found useful even in contact slide making, but it also requires not only good taste in the selection of the cloud, but some deftness in manipulation; but the neat-handed beginner need not fear to make the attempt.

DEVELOPMENT.

It has already been stated that judgment of exposure is a matter of experience, and that results are the best criterion; here follow some more explicit statements on the same matter.

Whatever plate or developer is used, and whatever the time occupied in complete development:

_1st._--If by the time the high-lights are sufficiently strong the shadows are too dense or blocked, the plate has been under-exposed.

_2nd._--If by the time the high-lights are sufficiently strong the shadows have not attained sufficient density, or are veiled, the plate has been over-exposed.

_3rd._--If at the same moment the high-lights show sufficiently and the shadows are transparent but sufficiently plucky, the plate has been properly exposed.

_4th._--With a normal negative the normal exposure is the proper exposure; but (_a_) a negative abnormally strong in contrasts will require an abnormally long exposure; and (_b_) a thin negative, or one with a very short scale of gradation from densest to clearest, will require an abnormally short exposure, with probably some after-treatment in the direction of "intensification."

Ambitious slide-makers generally aim at warm-toned slides for pictorial effect, and rightly. But slides intended for scientific purposes are generally better when cold in tone, the definition is usually better. But whatever the aim, a good tone of one kind is preferable to a poor one of another kind, and the beginner should first make sure of getting a really good cold tone, which is comparatively easy, and then try his "'prentice hand" on warm tones.

Warm tones are obtained by using greatly super-normal exposures and greatly restrained developers; and the danger probably lies in the fact that the long exposures are apt to lead to fog, and the great restraint to over-density in the shadows, the latter especially when the exposure has not been quite long enough for the developer used; herein probably lies the whole secret of warm slide-making. If we aim at really warm tones and use developers suited to such design, we must on no account stint the exposure.

COLD TONE DEVELOPING SOLUTIONS.

The classical solution for cold tone slides is a solution of ferrous oxalate in potassic oxalate. Of all developers it is most free from fogging propensities. It is made from so-called "saturated solutions" of proto-sulphate of iron and potassium oxalate. Thus, into a bottle put a quantity of iron proto-sulphate, and pour on about three times its weight of water containing a dram of sulphuric acid to each pint. Shake well, and keep always at about 60° Fahr.; some of the iron must always be visible in the bottle, if not, more is to be added. The crystals of iron salt must be green and not rusty in colour. This is the "iron solution."

The "oxalate solution" is made by dissolving potassium oxalate in about three times its weight of water. This also must be kept at 60° Fahr., shaken occasionally, and oxalate added if none is visible in the bottle.

To make the ferrous oxalate solution we _pour_ one part of the iron solution _into_ six parts of the oxalate, and it is advisable to add to each ounce of developer at least half a grain of potassium bromide; 5 minims of a 10% solution, made by dissolving one ounce of the bromide in about 9 ounces of water, and then making up to 10 ounces--all chemical.

In about four minutes or less this ought to fully develop a properly exposed plate. If the development is much shorter the slide is apt to have an unpleasant greenish tone, a result that may also follow the use of an inordinate amount of bromide in the developer. The developing solution may be made in quantity greater than is required for one plate, and may be used several times if a little of the surplus and fresh solution is added when the quantity in use becomes slow in action.

For really fine cold black tones the following formula by MESSRS. ELLIOTT & SON will be found admirable:--

A Metol 40 grains. Soda sulphite 1 ounce. Water 8 ounces.

B Potassium carbonate 120 grains. Ammonium bromide 24 " Potassium bromide 48 " Water 8 ounces.

The developing solution consists of equal parts of A and B.

If either of the above developers is to be used, the exposure is to be kept down as compared with the exposure to be followed by developers intended for very warm tones.

The two developers which follow next, require about the same exposure as the two already formulated. "Ortol" is a reducing agent quite lately introduced by Mr. Hauff, of Feuerbach in Germany, and Mr. Hauff's agents in this country are Messrs. Fuerst Bros., of London. "Ortol" gives the finest tones of the warm black type that we have as yet come across, it is singularly free from fogging propensity, and the tones do not easily degenerate into the greens so apt to occur after severe over-exposure with other "black" developers. We suggest a simple formula:--

A Water 20 ounces. Metabisulphite of potassium 75 grains. Ortol 150 grains.

B Water 20 ounces. Soda carbonate 3-1/2 ounces. Soda sulphite 2-1/2 ounces.

To make the developer, take one part of A, one of B, and one of water, and to each ounce of the mixture add one and a half or two grains of potassium bromide. The development of a properly exposed slide will take two or three minutes, and the result will probably be highly appreciated.

The above is worthy to stand alone as representing developers for warm black tones, but the following works well. (Messrs. Elliott & Son.)

A Hydroquinone 80 grains. Soda sulphite 1 ounce. Potassium bromide 15 grains. Water 10 ounces.

B Caustic soda 80 grains. Water 10 ozs.

The developing solution consists of equal parts of A and B, and the plate may be fully developed in about two to three minutes.

It has already been stated that in order to obtain really warm red or reddish tones by development, it is necessary to give very long exposure, and to use a developer very much restrained. It is further found that carbonate of ammonia has a considerable effect in reddening the developed image, and so we now come to procedure based on these lines. Carbonate of ammonia is found in commerce in the shape of "chunks" more or less square. If one of these is pared with a knife--unless the sample is quite fresh--the outside will be found to be a soft amorphous powder, the inside a clear, very hard crystal; the clear crystal is in development an "accelerator," though a very weak one, the outside substance is a restrainer. Probably both the inside--sesquicarbonate--and the outside--bicarbonate--are useful, and the best plan is to make a ten per cent. solution of the substance as obtained from a good chemist--not druggist. Of this solution one grain of the salt is represented by ten minims. If now we take an ounce of A, and one of B of the last formula, and if we add to the ounce of A 3 grains of ammonium bromide, and to the ounce of B 3 grains of ammonium carbonate, and if we have given a proper exposure and develop with equal parts of the A and B modified as above, we shall get a slide of rich chocolate colour; and if we double the proportions of carbonate and bromide, and expose still longer, we shall get a slide still ruddier in tone, even to red. But there is always danger of fog, and of clogged shadows, and this must be reckoned with. There is a more certain and less dangerous way of getting handsome tones, which shall be described presently.

Gelatine slides are always fixed in hyposulphite of soda, about one part by weight to six parts of water; after this they must be well washed, say five minutes under a good rose tap, or in many changes of water in a dish for an hour, and every slide should be treated with a saturated solution of potash alum, of which each pint should contain a dram of hydrochloric acid.

Very many, if not most, slides are all the better for just a touch of a "reducer" such as follows:--The ordinary "hypo." solution is weakened with about four times its measure of water, and the plate is soaked for a minute in this. A few drops of a ten per cent. solution of potassium ferricyanide are put into the measure, and the hypo. mixed with it, and the whole allowed to work on the plate for a short time, carefully watched. Of course a weak slide must not be thus treated, but it is often a good plan to develop slides to such a point that they will permit of this treatment.

On the other hand it is often advisable to keep a slide thin in development, for instance, when the negative wants pluck, and intensification is indicated; or when we wish a good warm tone after a "black" developer such as our metol formula: a good average treatment is as follows:--